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13.
Database Recovery, Backup, and Restoration
 13.1
Types of Database Failures
13.2
Recovery from Database Failures
13.3
Types of Backups
13.4
Backup Modes
13.5
Manual Backups
13.6
Automatic Backups
13.7
Backup History Files
13.8
Recovery Options
13. Database Recovery, Backup, and Restoration
In every
database management system, the possibility of a hardware or software
failure always exists. Although we would like to think otherwise, a
DBMS may fall victim to these types of failures without warning. After
a failure occurs, a DBMS should have some method of recovering the information
that was entered into the database. In fact, this is one of the main
advantages a DBMS has over the file-based systems they replaced.
DBMaker
incorporates advanced data protection features to prevent data loss
and down-time due to failures. These features allow DBMaker to ensure
the reliability of your database and the consistency of your data by
providing recovery, backup, and restoration features.
13.1 Types of Database Failures
Database
failures can generally be divided into two types: system failures and
media failures. When either of these types of failure occurs, there
is the possibility of data inconsistency or data loss in a database
that experiences a failure. A DBMS should provide facilities for recovering
from database failures and for replacing a damaged database with a backup
copy of the original.
System Failures
A system
failure (also known as instance failure) is a failure of the main memory
of a computer system. System failures may be caused by a power failure,
an application or operating system crash, a memory error, or some other
reason. The end result is the unexpected termination of the database
management system software.
When a
system failure occurs, applications and possibly active transactions
terminating abnormally. Since the exact state of a transaction in progress
or a transaction that has not been completely written to disk cannot
be reliably determined after a system failure, these types of transactions
require recovery. The most common method of protecting against system
failures is the use of a transaction log, or journal file.
Media Failures
Media failure
(also known as disk failure) is a failure of the disk storage system
of a computer system. Media failures are usually caused by physical
trauma to the disk itself, such as a head crash, fire, or exposure to
vibration or g-forces outside its physical operating limits.
When a
media failure occurs, there is generally nothing that can prevent the
loss of data on the affected disk. One or more files may be physically
damaged as a result of the failure, requiring restoration of the database.
However the database can be successfully restored if the database provides
backup and restoration facilities.
13.2 Recovery from Database Failures
The goals
of recovery after a database failure are to ensure committed transactions
are reflected in the database, ensure uncommitted transactions are not
reflected in the database, and to return to normal operation as quickly
as possible while insulting users from problems caused by the failure.
DBMaker
uses journal files and checkpoints to achieve these goals. The journal
files and checkpoints work together to ensure that all transactions
are recovered in a short a time as possible, with as little effect on
users as possible.
Journal Files
Journal
files provide a real-time, historical record of all changes made to
a database, and the status of each change. In the event of a system
failure, the historical record of changes maintained in the journal
file allows DBMaker to recover from the failure and redo changes made
by transactions that completed but were not written to disk, or undo
changes made by transactions that terminated abnormally.
If a database
is running in backup mode, the journal files will also store additional
information that DBMaker can use to restore a database after a media
failure. This information will remain in the journal files until they
are backed up; after you back up the journal files DBMaker will free
this space for use by new transactions. During the restoration process,
DBMaker will add the information from the backup journal files to a
backup copy of the database. This allows you to back up only the journal
files which contain the changes made to the database between full backups.
Checkpoint Events
A checkpoint
is a system event in which the database is brought to a clean state.
DBMaker writes all journal records and all dirty data pages from its
internal memory buffers to disk, and reclaims journal blocks that are
no longer required for backup or recovery purposes. DBMaker can reclaim
journal blocks that contain non-active transactions that completed before
the start of the oldest active transaction.
Startup
time after an instance failure is reduced after taking a checkpoint.
DBMaker writes the time of the last checkpoint and a list of all transactions
active at the time of the checkpoint to the journal file header. During
database recovery, DBMaker uses this information to determine which
transactions should be undone, which should be redone, and which should
be ignored.
DBMaker
will automatically take a checkpoint when the journal files are full
to try to reclaim some journal blocks to reuse. If the checkpoint cannot
reclaim enough space to complete the current transaction, the transaction
will be aborted. DBMaker will also automatically take a checkpoint when
the database starts and shuts down, and when you perform an online backup.
Database
Administrators can initiate a checkpoint manually by executing the CHECKPOINT
command. The optimal interval between two checkpoints depends on the
frequency of activity in the database, the average size of transactions,
and the size and number of journal files. Since these factors may vary
significantly from database to database, you may only be able to determine
the optimal interval through experience. Manual checkpoints reduce the
amount of time required to start, terminate, and back up a database,
as well as the possibility that you will encounter a full journal.
Checkpoints
may require a significant amount of time to complete, depending on the
size and number of transactions since the last checkpoint. Any transactions
that are active when a checkpoint occurs need to wait for DBMaker to
calculate which journal records it can reclaim, but do not need to wait
while DBMaker actually writes journal records and dirty data pages to
disk.
Recovery Steps
DBMaker
provides support for automatic recovery when you try to start a database
after a system failure, or when an error occurs during startup. During
the recovery process, DBMaker always performs two separate steps: redo
and undo.
The first
step in the recovery process is to redo (or reapply) all changes made
to the database that are recorded in the journal. This step is necessary
since it is possible for a transaction to have completed before the
system failure, without having all the changes made by the transaction
written to the database. However, these changes are stored in
the journal, and can be written to the database during this step. At
the end of this step, the database contains the changes made by all
committed transactions, as well as the changes made by all uncommitted
transactions.
The second
step in the recovery process is to undo (or roll back) all the changes
made by transactions that were not completed before the system failure
occurred. This step is necessary since the exact state of a transaction
in progress cannot be reliably determined in the event of a system failure,
so it cannot continue to completion. These incomplete transactions must
be removed since a transaction is self-contained by definition and must
either complete successfully and change the data, or fail and leave
the data unchanged. At the end of this step, the database contains the
changes made by all committed transactions, but does not contain any
changes made by uncommitted transactions.
DBMaker
also provides support for starting a database after a media failure
or after a system failure that causes inconsistencies in a database
that cannot be repaired during the automatic recovery process. In these
cases the database will fail to start, and you would normally need to
restore your database from a backup copy. However, if you have never
backed up your database, you can force the database to start by setting
the forced-start mode using the DB_FORCS keyword in the dmconfig.ini
configuration file. This will allow you to start the database and unload
the unaffected data. For more information on the forced-start mode,
see "Forcing Database Startup".
13.3 Types of Backups
Backups
are used to protect your database from media failures or other media
errors. After a media failure, one or more of your database files may
be physically damaged and unusable. You can use the most recent backup
to replace the damaged files and reconstruct your database in a case
like this.
There are
two main types of database backups: full backups and incremental backups.
In addition, there are also two different states your database may be
in when you want to perform a backup: online and offline. DBMaker supports
several different combinations of backup types and database states.
Full Backups
A full
backup is any backup that creates a copy of all data and journal files,
providing a copy of the entire database at one point in time. You can
optionally create a backup copy of the dmconfig.ini configuration file
as well, preserving any custom configuration settings you may have for
your database. DBMaker allows you to perform a full backup while your
database is online or offline.
Full backups
archive the entire database, so they require a large amount of storage
space. However, you can restore a database relatively quickly using
a full backup since you can simply copy the backup files over the damaged
originals. You can use a full backup to restore a database to the point
in time you performed the full backup and copied database files.
Incremental Backups
An incremental
backup is any backup that creates a copy of only the journal files that
have changed since the last backup. These files provide a copy of the
changes made to the database since the last backup. Since an incremental
backup only contains changes made to the database, you must perform
a full backup prior to the incremental database in order to restore
your database at a later time. DBMaker allows you to perform an incremental
backup only while your database is online.
Incremental
backups archive only journal files, so they require only a small amount
of storage space. However, it may take more time than a full backup
to restore a database since the DBMS must take the time to roll over
all transactions in the backup journal files. You can use an incremental
backup together with a full backup to restore a database to any point
in time between the time of the previous full backup to the time the
incremental backup completed.
Offline Backups
An offline
backup is any backup that must be performed after a database has been
shut down. The Database Administrator must schedule a time to shut down
the database, and notify all users so they can disconnect from the database.
Offline backups can be inconvenient for users, since they must remember
to complete all active transactions and disconnect from the database
before it is shut down. DBMaker can perform only full backups while
offline.
A DBMS
does not need to explicitly provide the capability to back up a database
offline, since you can back up the database with operating system commands
after it is shut down. DBMaker allows you to perform an offline backup
using this method, but also provides Server Manager, an easy-to-use
graphical tool that allows you to perform offline backups without resorting
to using operating system commands.
Online Backups
An online
backup is any backup that can be performed while a database is running.
The Database Administrator does not have to shut down the database,
and users do not need to disconnect. Online backups are more convenient
for users, since no action is required on their part. DBMaker can perform
full and incremental backups while online.
A DBMS
must explicitly provide the capability to back up a database online,
since it is still running and still has users connected. DBMaker allows
you to perform online backups manually using dmSQL and operating system
commands, but also provides Server Manager, an easy-to-use graphical
tool that allows you to perform online backups without resorting to
operating system commands.
Backup Combinations
You can
perform full backups and incremental backups using DBMaker, but they
are mutually exclusive; you cannot perform a full backup and an incremental
backup together. Similarly you can perform a backup while the database
is offline or online using DBMaker, but they are also mutually exclusive;
you cannot perform an offline backup and an online backup together.
However, DBMaker does allow you to mix full or incremental backups with
online or offline backups in certain combinations.
DBMaker
supports the following backup combinations: offline full backups, online
full backups, and online incremental backups. DBMaker also supports
an additional backup type known as online incremental to current.
The difference
between an online incremental backup and an online incremental to current
backup in a database with multiple journal files is minor, but important.
In an online incremental backup DBMaker will back up all journal files
that have been used since the last backup, excluding the active journal
file. In an online incremental to current backup DBMaker will back up
all journal files that have been used, including the active journal
file. This means that an online incremental backup can restore a database
up to the point in time the last committed transaction was written to
the last full journal file, while an online incremental to current backup
can restore a database up to the point in time the active journal file
was backed up.
In a database
with only a single journal file, an online incremental backup and an
online incremental to current backup are exactly the same. In this case
the only journal file is the active journal file. DBMaker will back
up this single journal file in both types of incremental backup.
13.4 Backup Modes
Backup
mode determines whether DBMaker can perform online incremental backups,
and the type of data that will be backed up during an incremental backup.
It also determines when DBMaker will free journal blocks that belong
to inactive transactions for use by other transactions. DBMaker has
three backup modes: NONBACKUP, BACKUP-DATA, and BACKUP-DATA-AND-BLOB.
NONBACKUP Mode
NONBACKUP
mode provides no protection for any data that was inserted or updated
since the last full backup. In this mode, a database cannot perform
online incremental backups. A database can use the journal to fully
recover from instance failure, but a media failure may result in loss
of data. Journal blocks not in use by an active transaction can be reused
immediately after a checkpoint, but once they are overwritten, you can
only restore the database to the point in time of the last full backup.
BACKUP-DATA Mode
BACKUP-DATA
mode provides protection for data (excluding BLOB data) that was inserted
or updated since the last full backup. In this mode, a database can
perform an online incremental backup, but only non-BLOB data will be
stored in the backup files. A database can use the journal to fully
recover from instance failure, and can partially recover from media
failure. Although you can use the last backup to restore the database
to the point in time of the media failure, any changes to BLOB data
will be lost. Journal blocks not in use by an active transaction can
only be reused after a checkpoint has taken place and the journal
file has been backed up.
BACKUP-DATA-AND-BLOB Mode
BACKUP-DATA-AND-BLOB
mode provides protection for all data (including BLOB data) that was
inserted or updated since the last full backup. In this mode, a database
can perform an online incremental backup, and all data will be stored
in the backup files. A database can use the journal to fully recover
from instance failure, and can also fully recover from disk failure.
You can use the last backup to completely restore the database to the
point in time of the media failure, including all BLOB data. Journal
blocks not in use by an active transaction can only be reused after
a checkpoint has taken place and the journal file has been backed
up.
Tablespace BLOB Backup Mode
DBMaker
normally applies the backup mode setting to the entire database; this
means all tablespaces in the database will be in the same backup mode.
If the database is in BACKUP-DATA-AND-BLOB mode DBMaker will record
all changes to data (including BLOB data) in the journal. Recording
BLOB data in the journal can quickly exhaust journal space, producing
frequent backups and large backup file sizes.
This may
be necessary if you cannot afford to lose any BLOB data, but in many
cases you may also be backing up non-critical BLOB data at the same
time. Situations like this make it difficult for you to decide which
backup mode you should choose. To prevent this type of situation from
occurring, DBMaker allows you to modify the database backup mode for
individual tablespaces when you create them.
If you
want to back up BLOB data in a specific tablespace, you can use the
BACKUP BLOB ON option when you execute the CREATE TABLESPACE command.
If you do not want to back up BLOB data in a specific tablespace, you
can use the BACKUP BLOB OFF option when you execute the CREATE TABLESPACE
command. The backup mode of each tablespace will then depend on the
combination of database backup mode and tablespace backup mode as follows:
If the database is running in BACKUP-DATA-AND-BLOB mode and a tablespace
was created with the BACKUP BLOB ON option, DBMaker will back up BLOB
data in that tablespace.
If the database is running in BACKUP-DATA-AND-BLOB mode and a tablespace
was created with the BACKUP BLOB OFF option, DBMaker will not back up
BLOB data in that tablespace.
If the database is running in BACKUP-DATA mode, DBMaker will not back
up BLOB data regardless of whether a tablespace was created with the
BACKUP BLOB ON or BACKUP BLOB OFF option.
If you
do not specify either the BACKUP BLOB ON or the BACKUP BLOB OFF option
when you create a tablespace, DBMaker will use BACKUP BLOB ON by default.
All changes to BLOB data in that tablespace will be recorded in the
journal file when the database is in BACKUP-DATA-AND-BLOB mode.
Setting the Backup Mode
DBMaker
provides several different methods to set the backup mode. The method
you choose depends on whether your database is online or offline, and
whether you are more comfortable editing the configuration file directly,
using the dmSQL command line utility, or using the Server Manager graphical
utility.
Modifying
the backup mode of a database to provide a higher level of backup protection
(i.e. from NONBACKUP to BACKUP-DATA mode, or from BACKUP-DATA to BACKUP-DATA-AND-BLOB
mode) has an effect on journal usage. The journal begins recording changes
to data that was previously not recorded prior to modifying the backup
mode. As a result, it is necessary to perform a full backup when you
change the backup mode. This provides a starting point for the backup
journal files to update during the restoration process.
No extra
steps are required when modifying the backup mode of a database to provide
a lower level of backup protection (i.e. from BACKUP-DATA or BACKUP-DATA-AND-BLOB
mode to NONBACKUP mode) since the journal simply stops recording changes
to data. DBMaker will use the previous full backup as a starting point
for the backup journal files to update during the restoration process.
However, some changes to data may be lost if you restore a database
after changing to a lower level of backup protection.
You can
change the backup mode of your database offline using the dmconfig.ini
configuration file or Server Manager. Since the backup mode affects
journal usage, you must perform an offline full backup before you start
the database with the new backup mode setting. When changing the backup
mode offline, you may change from any backup mode to any other backup
mode without restriction, providing you make a full backup when going
from a lower level of backup protection to a higher level. For more
information on performing an offline full backup, see "Performing
Offline Full Backups" later in this chapter.
You can
change the backup mode of your database online using dmSQL. Since the
backup mode will affect journal usage, you must change the backup mode
from a lower level of backup protection to a higher level (i.e. from
NONBACKUP to BACKUP-DATA or BACKUP-DATA-AND-BLOB mode, or from BACKUP-DATA
to BACKUP-DATA-AND-BLOB mode) between the start and finish of a full
backup period. For example:
dmSQL> begin backup;
dmSQL> set data backup on;
dmSQL> end backup datafile;
dmSQL> end backup journal;
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or
dmSQL> begin backup;
dmSQL> end backup datafile;
dmSQL> set data backup on;
dmSQL> end backup journal;
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DBMaker
does not allow you to go from a higher level of backup protection to
a lower level unless you change to NONBACKUP mode first. If you want
to change from BACKUP-DATA-AND-BLOB to BACKUP-DATA mode, you must first
change to NONBACKUP mode and then follow the rules above for changing
from a lower level of backup protection to a higher level. You may change
the backup mode from BACKUP-DATA-AND-BLOB or BACKUP-DATA to NONBACKUP
at any time; you do not need to do this between the start and finish
of a full backup period. For more information on performing an online
full backup, see "Performing Online Full Backups" later in
this chapter.
Using the dmconfig.ini Configuration File
If the
database is offline, you can change the backup mode directly using the
DB_BMODE keyword in the dmconfig.ini configuration file. The next time
you start the database, the new backup mode will be used. If the database
is online, changing the value of the DB_BMODE keyword will have no effect
until the database is shut down and restarted. You must remember to
perform an offline full backup if you are going from NONBACKUP to BACKUP-DATA
or BACKUP-DATA-AND-BLOB mode, or from BACKUP-DATA to BACKUP-DATA-AND-BLOB
mode.
To
set the backup mode using the dmconfig.ini configuration file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the backup mode.
3. Change
the value of the DB_BMODE keyword to one of the following values:
0 - NONBACKUP mode
1 - BACKUP-DATA mode
2 - BACKUP-DATA-AND-BLOB mode
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4. Restart
the database to begin using the new backup mode.
If the
DB_BMODE keyword is not present in the database configuration section
for the database you want to change the backup mode for, you will have
to add the DB_BMODE keyword to that database configuration section.
You can add the keyword on a separate line anywhere between the start
of the database configuration section and the start of the next configuration
section; the order the keywords appear in is not important. If you do
not specify a value for DB_BMODE, the default value of 0 (NONBACKUP
mode) will be used.
Using dmSQL
If the
database is online and you are comfortable using the dmSQL command line
utility, you can change the backup mode using the SQL SET command. You
must execute this command during an online full backup. The new backup
mode will be enabled as soon as the command is executed.
To
set the backup mode using the dmSQL command line utility:
1. Connect
to the database for which you want to change the backup mode using dmSQL.
2. Begin
an online full backup using the BEGIN BACKUP command.
3. Change
the backup mode during the full backup period by issuing one of the
following SET commands at the dmSQL command prompt:
dmSQL> set backup off;
dmSQL> set data backup on;
dmSQL> set blob backup on;
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4. Complete
the online full backup.
The SET
BACKUP OFF command corresponds to NONBACKUP mode, the SET DATA BACKUP
ON corresponds to BACKUP-DATA mode, and the SET BLOB BACKUP ON command
corresponds to BACKUP-DATA-AND-BLOB mode.
Using Server Manager
If the
database is offline, you can change the backup mode using the Server
Manager graphical utility. (Server Manager will automatically change
the value of the DB_BMODE keyword in the dmconfig.ini configuration
file. The next time you start the database, the new backup mode will
be used. If the database is online, changing the value of the DB_BMODE
keyword will have no effect until the database is shut down and restarted.
You must remember to perform an offline full backup if you are going
from NONBACKUP to BACKUP-DATA or BACKUP-DATA-AND-BLOB mode, or from
BACKUP-DATA to BACKUP-DATA-AND-BLOB mode.
To set the backup mode offline using the Server Manager graphical utility:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to change the backup mode. The Database Options tabs appear.
4. Select
the Backup tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Change
the backup mode by performing one of the following actions:
To
enable NONBACKUP mode, select the Disable option button in the Backup
Database frame.
To enable BACKUP-DATA mode, select the Enable option button and clear
the Backup BLOB Data Mode check box in the Backup Database frame.
To enable BACKUP-DATA-AND-BLOB mode, select the Enable option button
and select the Backup BLOB Data Mode check box in the Backup Database
frame.
7. Click
on the Close button.
If the
DB_BMODE keyword is not present in the database configuration section
for the database you want to change the backup mode for, Server Manager
will add it automatically.
13.5 Manual Backups
You can
perform offline full backups, online full backups, online incremental
backups, and online incremental to current backups manually using either
dmSQL or Server Manager.
Using dmSQL
to perform any of these backup procedures requires knowledge of the
commands or utilities your operating system uses to copy files from
one location to another. Server Manager provides a faster and easier
way to perform these backup procedures, since Server Manager will automatically
copy the all database files to the backup directory you specify, without
requiring you to perform any extra steps.
Performing Offline Full Backups
To perform
an offline full backup, you must have read permission on the database
files from the operating system, and write permission on the backup
directory from the operating system. If you have to shut down the database
first, you must have DBA or SYSADM security privileges.
You can
perform an offline full backup regardless of the backup mode; the database
may be running in NON-BACKUP, BACKUP-DATA, or BACKUP-DATA-AND-BLOB mode.
Using an offline full backup, you can restore the database to the point
in time the database was shut down.
Using dmSQL
To perform an offline full backup using dmSQL:
1. Notify
all users that the database will be shut down at a specified time and
ask them to disconnect from the database before that time.
2. If the
database is running, shut down the database using the TERMINATE DB command.
If there are any errors while you are shutting down the database, you
must restart the database, correct the problem, and shut it down again.
3. Examine
the dmconfig.ini configuration file and list all relevant files and
directories (including the file object directory) that require backup.
4. Use
operating system commands or utilities to copy the database files (including
data files, journal files, file objects, and the dmconfig.ini file)
to the backup directory or backup device.
Using Server Manager
To perform an offline full backup using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. If the
database is running, shut down the database using Server Manager. If
there are any errors while you are shutting down the database, you must
restart the database, correct the problem, and shut it down again.
3. From
the Database menu, choose Backup and then choose Offline Full Backup
from the submenu. The Offline Full Backup dialog box appears.
4. In the
Database Name drop-down list, choose the name of the database you want
to back up. A list of database files that require backup appears.
5. Examine
the list of files to ensure that the files listed in the Database Files
and Destination Files columns are correct, and that the backup directory
is correct.
6. Click
OK to back up the files.
7. Examine
the dmconfig.ini configuration file and determine the location of the
file object directory.
8. Use
operating system commands or utilities to copy all file objects to the
backup directory or backup device.
Performing Online Full Backups
To perform
an online full backup, you must have DBA or SYSADM security privileges.
An online full backup allows you to back up all files without requiring
other users to disconnect and without shutting down the database. This
is feature is important for databases where continuous, uninterrupted
access is required.
You can
perform an online full backup regardless of the backup mode; the database
may be running in NON-BACKUP, BACKUP-DATA, or BACKUP-DATA-AND-BLOB mode.
Using an online full backup, you can restore the database to any time
between the time the END BACKUP DATAFILE was executed to the time the
active journal file was copied.
Using dmSQL
To perform an online full backup using dmSQL:
1. Examine
the dmconfig.ini configuration file and list all relevant files and
directories (including the file object directory) that require backup.
2. Connect
to the database you want to back up.
3. Execute
the BEGIN BACKUP command to begin the backup and place the database
in the backup state.
4. Use
operating system commands or utilities to copy all data and BLOB files
to the backup directory or backup device.
5. Execute
the END BACKUP DATAFILE command to inform DBMaker that all data and
BLOB files have been backed up. This is the earliest point in time that
the database can be restored to.
6. Use
operating system commands or utilities to copy all journal files to
the backup directory or backup device.
7. Execute
the END BACKUP JOURNAL command to inform DBMaker that all journal files
have been backed up. If the database is operating in BACKUP-DATA or
BACKUP-DATA-AND-BLOB mode, DBMaker can reuse all journal blocks belonging
to transactions that have completed before the oldest active transaction
after the END BACKUP JOURNAL command is issued.
8. Disconnect
from the database.
9. Use
operating system commands or utilities to copy any file objects to the
backup directory or device.
Using Server Manager
To perform an online full backup using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Database menu, choose Backup and then choose Online Full Backup
from the submenu. The Online Full Backup dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database you want
to back up. A list of database files that require backup appears.
4. Examine
the list of files to ensure that the files listed in the Database Files
and Destination Files columns are correct, and that the backup directory
is correct.
5. Click
OK to back up the files.
6. Examine
the dmconfig.ini configuration file and determine the location of the
file object directory.
7. Use
operating system commands or utilities to copy all file objects to the
backup directory or backup device.
Performing Online Incremental Backups
To perform
an online incremental backup, you must have DBA or SYSADM security privileges.
An online incremental backup allows you to back up only those journal
files that have changed since the last backup (excluding the journal
file currently in use), without requiring other users to disconnect
and without shutting down the database.
You can
perform an online incremental backup only if the database is running
in BACKUP-DATA or BACKUP-DATA-AND-BLOB mode. Using an online incremental
backup, you can restore the database to any time between the time the
END BACKUP DATAFILE was executed during the previous full backup, to
the time the last committed transaction was written to the last full
journal file.
Using dmSQL
To perform an online incremental backup using dmSQL:
1. Connect
to the database you want to back up.
2. Execute
the BEGIN INCREMENTAL BACKUP command to begin the backup and place the
database in the backup state.
3. Record
the names of the journal files and the backup identification number
for each file that is displayed by dmSQL. You should keep this list
in a safe place as a permanent record. If you have previously performed
an online incremental backup using dmSQL, you can append this list to
the end of the previous list.
4. Use
operating system commands or utilities to copy all journal files in
the list to the backup directory or backup device.
5. Execute
the END BACKUP JOURNAL command to inform DBMaker that all journal files
have been backed up. DBMaker can reuse all journal blocks belonging
to transactions that have completed before the oldest active transaction
after the END BACKUP JOURNAL command is issued.
6. Disconnect
from the database.
7. Examine
the dmconfig.ini configuration file and determine the location of the
file object directory.
8. Use
operating system commands or utilities to copy any file objects that
have been added or modified since the last full backup to the backup
directory or device.
Using Server Manager
To perform an online incremental backup using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Database menu, choose Backup and then choose Online Incremental
Backup from the submenu. The Online Incremental Backup dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database you want
to back up. A list of journal files that require backup appears.
4. Examine
the list of files to ensure that the files listed in the Journal Files
and Destination Files columns are correct, and that the backup directory
is correct.
5. Click
OK to back up the files.
6. Examine
the dmconfig.ini configuration file and determine the location of the
file object directory.
7. Use
operating system commands or utilities to copy any file objects that
have been added or modified since the last full backup to the backup
directory or device.
Performing Online Incremental to Current Backups
To perform
an online incremental to current backup, you must have DBA or SYSADM
security privileges. An online incremental to current backup allows
you to back up all journal files that have changed since the last backup
(including the journal file currently in use), without requiring other
users to disconnect and without shutting down the database.
You can
perform an online incremental to current backup only if the database
is running in BACKUP-DATA or BACKUP-DATA-AND-BLOB mode. Using an online
incremental to current backup, you can restore the database to any time
between the time the END BACKUP DATAFILE was executed during the previous
full backup, to the time the active journal file was copied.
Using dmSQL
To perform an online incremental backup to current using dmSQL:
1. Connect
to the database you want to back up.
2. Execute
the BEGIN INCREMENTAL BACKUP TO CURRENT command to begin the backup
and place the database in the backup state.
3. Record
the names of the journal files and the backup identification number
for each file that is displayed by dmSQL.
4. Use
operating system commands or utilities to copy all journal files in
the list to another location.
5. Execute
the END BACKUP JOURNAL command.
6. Disconnect
from the database.
7. Examine
the dmconfig.ini configuration file and determine the location of the
file object directory.
8. Use
operating system commands or utilities to copy any file objects that
have been added or modified since the last full backup to the backup
directory or device.
Using Server Manager
To perform an online incremental backup to current using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Database menu, choose Backup and then choose Online Incremental
Backup to Current from the submenu. The Online Incremental Backup to
Current dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database you want
to back up. A list of journal files that require backup appears.
4. Examine
the list of files to ensure that the files listed in the Journal Files
and Destination Files columns are correct, and that the backup directory
is correct.
5. Click
OK to back up the files.
6. Examine
the dmconfig.ini configuration file and determine the location of the
file object directory.
7. Use
operating system commands or utilities to copy any file objects that
have been added or modified since the last full backup to the backup
directory or device.
13.6 Automatic Backups
Although
DBMaker provides several tools and methods for backing up a database
manually, you must still remember to perform the backups on a regular
basis. Depending on your memory to back up your database may not provide
a reliable safeguard for your data, since even the most reliable people
may forget things on occasion. To solve this problem, DBMaker provides
a convenient and easy way to perform fully automated online incremental
backups using Backup Server.
Backup
Server runs in the background and performs online incremental backups
on a regular schedule, as journal files become full, or both. This flexibility
is possible because Backup Server and the database server communicate
to determine when a backup should occur, the type of incremental backup
to perform, and which backup options to change. Backup Server starts
at the same time as the database server, and continues running until
you either stop it or shut down the database server.
There are
several options you can use to configure Backup Server. These options
control the filename format of the backup files, the location of the
backup directory, the schedule Backup Server uses to perform backups,
the amount a journal file must fill before Backup Server performs a
backup, and the way Backup Server saves backup files.
Setting the Backup Filename Format
The backup
filename format allows you to specify the format Backup Server will
use to name backup journal files. This enables you to provide meaningful
names for the backup files, making them easier to identify when you
are restoring a database. The backup filename format may include both
text constants and format sequences (escape sequences) that represent
special character strings.
You can
use the format sequences to represent the year, month, or date the backup
was performed on, the name of the database, or the backup identification
number. You may combine format sequences and text constants in any way,
provided the result is a valid filename for the operating system you
are using. The format sequences have three parts: the escape character,
the length value, and the format character. The valid format sequences
are:
%[n]Y - The year the journal file was backed up.
%[n]M - The month the journal file was backed up.
%[n]D - The day the journal file was backed up.
%[n]B - The backup identification number.
%[n]N - The name of the database the journal file belongs
to.
The escape
character identifies the start of the format sequence, and is represented
by the % symbol. If you want to include the % symbol as a text constant
in the backup filename format, you must use two % symbols together (i.e.
%%). A single digit or one of the valid format characters shown above
must immediately follow the % symbol. If any other characters follow
the % symbol the backup filename format is invalid, and DBMaker will
return an error.
The length
value is an integer value between one and nine that determines the length
of the character string generated by the format sequence. If the format
sequence returns a string that can be represented in fewer characters
than the length value provides, it will be expanded by adding zeroes.
The database name has zeroes added to the right of the name, while all
other values have zeroes added to the left. If the format sequence returns
a string that requires more characters than the length value provides,
it will be truncated. The database name is truncated from the right,
while all other values are truncated from the left. The square brackets
enclosing the length value indicate the length value is optional; do
not include the square brackets when entering the format sequence. If
you do not provide a value for the length, Backup Server will use the
full length of the character string generated by the format sequence.
The format
character identifies the type of special character string the format
sequence will return. The format character must be one of Y, M, D, B,
or N; using any other character will result in an invalid backup filename
format, and DBMaker will return an error. A valid format character that
does not immediately follow either the escape character or the escape
character and a single digit will be treated as a text constant.
The values
for the year, month, and date are taken from the system date, and will
only be correct if the system date is correct. The value for the backup
identification number is the ordinal position of the backup journal
file in the backup sequence. DBMaker automatically provides this number
for each journal file that is backed up by Backup Server.
The backup
filename format is specified by the DB_BKFRM keyword in the dmconfig.ini
configuration file. If you do not specify a backup filename format,
Backup Server will use the default format: %4N%4B.JNL. The total length
of the filename returned by the backup filename format must not exceed
79 characters in length.
DBMaker
provides several different methods to set the backup filename format.
The method you choose depends on whether you are more comfortable editing
the configuration file directly or using the Server Manager graphical
utility.
Using dmconfig.ini
If the
database is offline, you can set the backup filename format used by
Backup Server directly using the DB_BKFRM keyword in the dmconfig.ini
configuration file. The next time you start the database, Backup Server
will apply this backup filename format to all backup journal files.
If the database is online, changing the value of the DB_BKDIR keyword
will have no effect until the database is shut down and restarted.
To set the backup file format using the dmconfig.ini configuration file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the backup directory.
3. Change
the value of the DB_BKFRM keyword to a string containing the format
you want to use for the backup filename format. The string may contain
any valid format sequences and text constants, but the total length
of the resulting filename must not exceed 79 characters in length.
4. Restart
the database to begin using the new backup filename format.
Using Server Manager
If the
database is offline or online, you can set the backup filename format
used by Backup Server using the Server Manager graphical utility. (Server
Manager will automatically change the value of the DB_BKFRM keyword
in the dmconfig.ini configuration file.) The next time you start the
database, Backup Server will apply this backup filename format to all
backup journal files.
To set the backup file format using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup filename format. The Database Options tabs
appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Enter
a valid backup filename format in the Filename Format text box in the
Backup Database frame.
7. Click
on the Close button.
If the
DB_BKFRM keyword is not present in the database configuration section
for the database you want to set the backup directory for, Server Manager
will add it automatically.
Setting The Backup Directory
The backup
directory specifies where the Backup Server will place all backup journal
files. The backup directory must be a directory that already exists;
if the directory you wish to use does not exist, you must create it
using operating system commands before you specify it as the backup
directory. You should choose a backup directory on a different disk
than the database files to prevent the loss of both the database and
the backup files in the event of a media error.
The backup
directory is specified by the DB_BKDIR keyword in the dmconfig.ini configuration
file. The value of the DB_BKDIR keyword may contain either a full or
relative path to the backup directory. If you do not specify a backup
directory, the Backup Server will automatically create a default backup
directory named "backup" under the database directory. (The
database directory is specified by the DB_DBDIR keyword in the dmconfig.ini
configuration file.) The total length of the backup directory path must
not exceed 79 characters in length.
It is not
a good idea to allow the Backup Server to create and use the default
backup directory if you have more than one database in the same directory.
In this case the backup history information from one database may overwrite
or append to the backup history information from another database, rendering
one or both of the backups unusable. To avoid this type of problem you
can put each database in a different database directory, or explicitly
specify a backup directory for each database. Placing each database
in a different database directory is the preferred method, since this
allows you to see exactly which files belong to which database.
DBMaker
provides several different methods to set the backup directory. The
method you choose depends on whether your database is online or offline,
and whether you are more comfortable editing the configuration file
directly or using the Server Manager graphical utility.
Using dmconfig.ini
If the
database is offline, you can set the backup directory used by Backup
Server directly using the DB_BKDIR keyword in the dmconfig.ini configuration
file. The next time you start the database, Backup Server will use this
directory as the backup directory. If the database is online, changing
the value of the DB_BKDIR keyword will have no effect until the database
is shut down and restarted.
To set the backup directory using the dmconfig.ini configuration file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the backup directory.
3. Change
the value of the DB_BKDIR keyword to a string containing the name of
an existing directory to set the backup directory.
4. Restart
the database to begin using the new backup directory.
Using Server Manager
If the
database is offline, you can set the backup directory used by Backup
Server using the Server Manager graphical utility. (Server Manager will
automatically change the value of the DB_BKDIR keyword in the dmconfig.ini
configuration file.) The next time you start the database, Backup Server
will use this directory as the backup directory. If the database is
online, Server Manager can change the backup directory immediately or
delay the change until the next time you restart the database. In either
case, Server Manager will also make a copy of the backup history file
in the new backup directory.
To set the backup directory while offline using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Click
on the browse button to the right of the Backup Directory text box in
the Backup Server frame. The Select Directory dialog box appears.
7. Select
the directory you want to use as the backup directory in the Select
Directory dialog.
8. Click
on the Select button.
9. Click
on the Close button.
To set the backup directory while online using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Set Run-Time Status check box if it is not already selected. The
Write to Config File check box may be selected or cleared. Server Manager
will always write a new value for the DB_BKDIR keyword in the dmconfig.ini
configuration file when the Set Run-Time Status check box is selected.
6. Click
on the browse button to the right of the Backup Directory text box in
the Backup Server frame. The Select Directory dialog box appears.
7. Select
the directory you want to use as the backup directory in the Select
Directory dialog.
8. Click
on the Select button.
9. Click
on the Close button.
If the
DB_BKDIR keyword is not present in the database configuration section
for the database you want to set the backup directory for, Server Manager
will add it automatically.
Setting the Backup Schedule
The backup
schedule specifies the times when Backup Server will perform an online
incremental backup. The backup schedule is composed of two parts: the
initial backup time and the interval time. The initial backup time determines
the date and time Backup Server will perform the first backup, and the
interval time determines the length of time to wait between subsequent
backups.
You can
combine the backup schedule with the journal trigger value to back up
your database both on a regular schedule and also when journal files
fill to a specified percentage. If you do not specify a backup schedule,
Backup Server will not back up the database on a regular schedule. However,
Backup Server will continue to back up the database as journal files
fill even without a backup schedule.
The initial
backup time is specified by the DB_BKTIM keyword in the dmconfig.ini
configuration file. You must enter the value of the DB_BKTIM keyword
as a date and time in the format YY/MM/DD HH:MM:SS. There is no default
value for the initial backup time. However, if you use Server Manager
to enable Backup Server, Server Manager will provide a default value
for you and write this value into the dmconfig.ini configuration file.
The interval
time is specified by the DB_BKITV keyword in the dmconfig.ini configuration
file. You must enter the value of the DB_BKITV keyword as a time interval
in the format D-HH:MM:SS. There is no default value for the interval
time. However, if you use Server Manager to enable Backup Server, Server
Manager will provide a default value of 1-00:00:00 for you and write
this value into the dmconfig.ini configuration file.
DBMaker
provides several different methods to set the backup schedule. The method
you choose depends on whether your database is online or offline, and
whether you are more comfortable editing the configuration file directly
or using the Server Manager graphical utility.
Using dmconfig.ini
If the
database is offline, you can set the backup schedule used by Backup
Server directly using the DB_BKTIM and DB_BKITV keywords in the dmconfig.ini
configuration file. The next time you start the database, Backup Server
will use these settings for the backup schedule. If the database is
online, changing the value of the DB_BKTIM and DB_BKITV keywords will
have no effect until the database is shut down and restarted.
To set the backup schedule using the dmconfig.ini configuration file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the backup schedule.
3. Change
the value of the DB_BKTIM keyword to a date and time. This value should
be in YY/MM/DD HH:MM:SS format.
4. Change
the value of the DB_BKITV keyword to a time interval. This value should
be in DDDDD-HH:MM:SS format.
5. Restart
the database to begin using the new backup schedule.
Using Server Manager
If the
database is offline, you can set the backup schedule used by Backup
Server using the Server Manager graphical utility. (Server Manager will
automatically change the value of the DB_BKTIM and DB_BKITV keywords
in the dmconfig.ini configuration file.) The next time you start the
database, Backup Server will use these settings as the new backup schedule.
If the database is online, Server Manager can change the backup schedule
immediately or delay the change until the next time you restart the
database.
To set the backup schedule while offline using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Click
on the browse button to the right of the Interval Time text box in the
Backup Server frame. The Change Backup Server Beginning Time and Interval
dialog box appears.
7. Enter
a value for the initial backup time in the New Beginning Time text box.
This value should be in YY/MM/DD HH:MM:SS format.
8. Enter
a value for the interval time in the Time Interval text box. This value
should be in D-HH:MM:SS format.
9. Click
on the OK button.
10. Click
on the Close button.
If the
DB_BKTIM and DB_BKITV keywords are not present in the database configuration
section for the database you want to set the backup schedule for, Server
Manager will add them automatically.
To set the backup schedule while online using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Set Run-Time Status check box if it is not already selected. Set
the Write to Config File check box if you want to use the initial backup
time and interval time settings every time you start the database, or
clear the Write to Config File check box if you only want to use the
settings for this session.
6. Click
on the browse button to the right of the Interval Time text box in the
Backup Server frame. The Change Backup Server Beginning Time and Interval
dialog box appears.
7. Enter
a value for the initial backup time in the New Beginning Time text box.
This value should be in YY/MM/DD HH:MM:SS format.
8. Enter
a value for the interval time in the Time Interval text box. This value
should be in D-HH:MM:SS format.
9. Click
on the OK button.
10. Click
on the Close button.
Setting the Journal Trigger Value
The journal
trigger value specifies the percentage a journal file must fill before
Backup Server will perform an online incremental backup. You can combine
the journal trigger value with the backup schedule to back up your database
on a regular schedule and when journal files fill to the specified percentage.
The journal
trigger value is specified by the DB_BKFUL keyword in the dmconfig.ini
configuration file. The value of the DB_BKFUL keyword may be an integer
value in the range 50-100, or zero. Values between 50-100 represent
the percentage a journal file must fill before Backup Server performs
a backup. A value of zero causes Backup Server to perform a backup whenever
a journal file fills completely. Setting the value to 0 is effectively
the same as setting it to a value of 100, since both will cause Backup
Server to perform a backup whenever a journal file fills completely
(100% full). If you do not specify a value for the journal trigger value,
Backup Server will use the default value of zero.
DBMaker
provides several different methods to set the journal trigger value.
The method you choose depends on whether your database is online or
offline, and whether you are more comfortable editing the configuration
file directly or using the Server Manager graphical utility.
Using dmconfig.ini
If the
database is offline, you can set the journal trigger value used by Backup
Server directly using the DB_BKFUL keyword in the dmconfig.ini configuration
file. The next time you start the database, Backup Server will use this
setting for the journal trigger value. If the database is online, changing
the value of the DB_BKFUL keyword will have no effect until the database
is shut down and restarted.
To set the journal trigger value using the dmconfig.ini configuration
file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the journal trigger value.
3. Change
the value of the DB_BKFUL keyword to an integer value between 50-100,
or zero.
4. Restart
the database to begin using the new journal trigger value.
Using Server Manager
If the
database is offline, you can set the journal trigger value used by Backup
Server using the Server Manager graphical utility. (Server Manager will
automatically change the value of the DB_BKFUL keyword in the dmconfig.ini
configuration file.) The next time you start the database, Backup Server
will use this setting as the new journal trigger value. If the database
is online, Server Manager can change the journal trigger value immediately
or delay the change until the next time you restart the database.
To set the journal trigger value while offline using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Enter
a value for the journal trigger value in the User-Defined Trigger Value
text box. This value should be in the range 50-100.
7. Click
on the Close button.
If the
DB_BKFUL keyword is not present in the database configuration section
for the database you want to set the journal trigger value for, Server
Manager will add it automatically.
To set the journal trigger value while online using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Set Run-Time Status check box if it is not already selected. Set
the Write to Config File check box if you want to use the journal trigger
value setting every time you start the database, or clear the Write
to Config File check box if you only want to use the setting for this
session.
8. Enter
a value for the journal trigger value in the User-Defined Trigger Value
text box. This value should be in the range 50-100.
6. Click
on the Close button.
Setting the Compact Backup Mode
Compact
backup mode specifies whether Backup Server will back up entire journal
files or only full journal blocks when it performs an online incremental
backup. This is possible since not every journal block contains data
needed to restore a database, so Backup Server will only back up the
necessary journal blocks when it performs a backup. This allows you
to save storage space on your backup device, but it also means restoring
a database may take more time.
The compact
backup mode setting is specified by the DB_BKCMP keyword in the dmconfig.ini
configuration file. The value of the DB_BKCMP keyword may be zero or
one. Setting the value to one enables compact backup mode, and setting
it to zero disables compact backup mode. If you do not specify a value
for the compact backup mode, Backup Server will use the default value
of one (enabled).
DBMaker
provides several different methods to set the compact backup mode. The
method you choose depends on whether your database is online or offline,
and whether you are more comfortable editing the configuration file
directly or using the Server Manager graphical utility.
Using dmconfig.ini
If the
database is offline, you can set the compact backup mode setting used
by Backup Server directly using the DB_BKCMP keyword in the dmconfig.ini
configuration file. The next time you start the database, Backup Server
will use this setting for the compact backup mode. If the database is
online, changing the value of the DB_BKCMP keyword will have no effect
until the database is shut down and restarted.
To set the journal trigger value using the dmconfig.ini configuration
file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the journal trigger value.
3. Change
the value of the DB_BKCMP keyword to a one to enable compact backup
mode, or zero to disable compact backup mode.
4. Restart
the database to begin using the new journal trigger value.
Using Server Manager
If the
database is offline, you can set the compact backup mode setting used
by Backup Server using the Server Manager graphical utility. (Server
Manager will automatically change the value of the DB_BKCMP keyword
in the dmconfig.ini configuration file.) The next time you start the
database, Backup Server will use this setting as the new compact backup
mode setting. If the database is online, Server Manager can change compact
backup mode setting immediately or delay the change until the next time
you restart the database.
To set the compact backup mode while offline using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Select
the Use Compact Backup Mode check box to enable compact backup mode.
Clear this check box to disable compact backup mode.
7. Click
on the Close button.
If the
DB_BKCMP keyword is not present in the database configuration section
for the database you want to set the compact backup mode for, Server
Manager will add it automatically.
To set the compact backup mode while online using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to set the backup directory. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Set Run-Time Status check box if it is not already selected. Set
the Write to Config File check box if you want to use compact backup
mode every time you start the database, or clear the Write to Config
File check box if you only want to use it for this session.
6. Select
the Use Compact Backup Mode check box to enable compact backup mode.
Clear this check box to disable compact backup mode.
7. Click
on the Close button.
Starting The Backup Server
DBMaker
will only start Backup Server if your database is in BACKUP-DATA or
BACKUP-DATA-AND-BLOB mode and the value of the DB_BKSVR keyword is set
to 1 in the dmconfig.ini configuration file. Backup Server will not
start if your database is in NONBACKUP mode or if the value of the DB_BKSVR
keyword is set to 0.
You do
not have to explicitly start Backup Server after setting the DB_BKSVR
keyword, since DBMaker will automatically start Backup Server while
starting the database. Backup Server is disabled by default.
Using dmconfig.ini
If the
database is offline, you can enable Backup Server directly using the
DB_BKSVR keyword in the dmconfig.ini configuration file. The next time
you start the database, Backup Server will also start. If the database
is online, changing the value of the DB_BKSVR keyword will have no effect
until the database is shut down and restarted.
To start Backup Server using the dmconfig.ini configuration file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to enable Backup Server.
3. Ensure
the backup mode of the database is either BACKUP-DATA or BACKUP-DATA-AND-BLOB
mode. The database is in BACKUP-DATA mode if the value of DB_BMODE is
set to 1, and it is in BACKUP-DATA-AND-BLOB mode if the value of DB_BMODE
is set to 2. For more information on setting the backup mode, see the
section titled "Setting the Backup Mode" earlier in this chapter.
4. Change
the value of the DB_BKSVR keyword to 1 to enable Backup Server.
5. Restart
the database to begin using Backup Server.
Using Server Manager
If the
database is offline, you can enable Backup Server using the Server Manager
graphical utility. (Server Manager will automatically change the value
of the DB_BKSVR keyword in the dmconfig.ini configuration file.) The
next time you start the database, Backup Server will also start. If
the database is online, enabling Backup Server will have no effect until
the database is shut down and restarted.
To start Backup Server while offline using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to enable Backup Server. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Ensure
the backup mode of the database is either BACKUP-DATA or BACKUP-DATA-AND-BLOB.
The database is in BACKUP-DATA mode if the Enabled option button is
selected in the Backup Database frame, and it is in BACKUP-DATA-AND-BLOB
mode if both the Enabled option button and the Backup BLOB Data Mode
check box are selected in the Backup Database frame. For more information
on setting the backup mode, see the section titled "Setting the
Backup Mode" earlier in this chapter.
7. Select
the Start option button in the Backup Server frame.
8. Click
on the Close button.
If the
DB_BKSVR keyword is not present in the database configuration section
for the database you want to enable Backup Server for, Server Manager
will add it automatically.
Stopping The Backup Server
You must
explicitly stop Backup Server when you no longer want it to run by setting
the value of the DB_BKSVR keyword to zero. However, Backup Server will
continue running until you shut down your database and restart it.
Using dmconfig.ini
If the
database is offline, you can disable Backup Server directly using the
DB_BKSVR keyword in the dmconfig.ini configuration file. The next time
you start the database, Backup Server will not start. If the database
is online, changing the value of the DB_BKSVR keyword will have no effect
until the database is shut down and restarted.
To stop Backup Server using the dmconfig.ini configuration file:
1. Open
the dmconfig.ini configuration file on the computer on which the database
server is located using any ASCII text editor.
2. Locate
the database configuration section for the database for which you want
to change the backup mode.
3. Change
the value of the DB_BKSVR keyword to 0 to disable the Backup Server.
4. Restart
the database.
Using Server Manager
If the
database is offline, you can disable Backup Server using the Server
Manager graphical utility. (Server Manager will automatically change
the value of the DB_BKSVR keyword in the dmconfig.ini configuration
file.) The next time you start the database, Backup Server will not
start. If the database is online, disabling Backup Server will have
no effect until the database is shut down and restarted.
To stop Backup Server while offline using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to disable Backup Server. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Write to Config File check box if it is not already selected. Clear
the Set Run-Time Status check box if it is not already cleared.
6. Select
the Stop option button in the Backup Server frame.
7. Click
on the Close button.
To stop Backup Server while online using Server Manager:
1. Start
the Server Manager application on the computer on which the database
server is located.
2. From
the Option menu, choose Database. The Database Options dialog box appears.
3. In the
Database Name drop-down list, choose the name of the database for which
you want to disable Backup Server. The Database Options tabs appear.
4. Select
the Backup/Restore tab.
5. Select
the Set Run-Time Status check box if it is not already selected. Set
the Write to Config File check box if you want to disable Backup Server
for future sessions. Clear the Write to Config File check box if you
want to disable Backup Server only for this session.
6. Select
the Stop option button in the Backup Server frame.
7. Click
on the Close button.
13.7 Backup History Files
Manual
incremental backups require you to note which journal files were backed
up, when they were backed up, and where the backup files are located.
This information may be misplaced or lost if you are not careful. Automatic
backups using the backup server prevent this by automatically storing
this information in the backup history file.
If you
perform an incremental backup manually, you should note which journal
files are backed up, when they were backed up, and where they the backup
files are located. If you start the backup server, it will record all
this information in a text backup history file.
Locating the Backup History File
This file
is created in the backup path and is named dmBackup.his.
This file will automatically be used during restoration of a database.
Understanding the Backup History File
Backup
history files are composed of a number of lines. Every line has the
following format:
<backup_id>: journal_file_name -> archive_file_name: time: event
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This denotes
that a journal file named journal_file_name was copied to an
archive file named archive_file_name at time because of
event. The event is a text string indicating the reason
for the backup. This string can be either JOURNAL-FULL or TIME-OUT.
The string JOURNAL-FULL indicates an incremental backup was performed
because the journal was full. The string TIME-OUT indicates an incremental
backup was performed because the scheduled backup interval has elapsed.
Using the Backup History File
If the
journal full situation occurs frequently, this means you should lower
the backup journal full percentage or shorten the time interval. You
can also find out if the backup interval is too short by checking the
backup history file. If the same journal file is backed up consecutively
in the backup history file, the time interval may be too short. This
situation will waste disk space because each file may only contain a
few changed blocks. To avoid this situation, you can enable compact
backup mode or lengthen the backup time interval.
If many
journal files are backed up every time, it may mean the time interval
is too long. This situation is more dangerous because of the possibility
of losing more data when a disk fails. Ideally, one journal file should
be backed up every time an incremental backup occurs. This will save
storage space and lower the risk of losing journal data.
To shorten
the time of recovery from media failures, perform full backups regularly,
even if you are using the backup server. In addition, this will also
reduce the amount of backup storage needed.
After the
backup server is running, you still can perform incremental backups
manually. As stated above, you should note the backup ID, time, and
location for the backup files.
13.8 Recovery Options
Restoring
a database will recreate the database as it existed at the time of your
most recent full backup, plus any changes that have been made in journal
files that have been backed up.
Analyzing Recovery Options
What recovery operation are available?
The answer
to this question is determined by whether or not your database is in
BACKUP mode. If the database is operating in NONBACKUP mode, the only
option for restoration after a disk failure is to restore the most recent
full backup and restart the database. All work performed since the last
full backup will be lost, and must be re-entered. If this is the case,
there is no need to answer the following questions.
If the
database is operated in BACKUP (BACKUP-DATA or BACKUP-DATA-AND-BLOB)
mode, several recovery options are available for reconstructing the
damaged database.
Preparing for Restoration
Before
you restore your database after a disk error, you must answer the following
questions:
What point in time do you want your database restored to?
If your
answer is the time when the disk error occurs, backup all journal files
of the damaged database if you can. These files will help DBMaker to
restore the database to the most current time.
What files have you previously backed up?
Find out
where the most current full backup and all subsequent incremental backups
are located. For example, suppose you perform a full backup on the 30th
day of every month and an incremental backup every 10 days. If your
system is damaged on May 25, you need the full backup from April 30,
the incremental backups from May 10 and May 20, and the damaged journal
files from May 25. After locating these files, DBMaker can restore your
database to the state it was in previous to the failure on May 25. Since
all online backup information is stored in the backup history file,
DBMaker will read it to get this information when restoring a database.
Performing a Restoration
DBMaker
uses Server Manager to perform restoration. The following procedure
is used to restore a database:
Server Manager copies all files of the most recent full backup (includes
BLOB files, data files, journal files and dmconfig.ini) to the directory
specified by the DB_DBDIR keyword in dmconfig.ini.
Set the time you want to restore the database to if you want to re-create
the state the database was in at a specific point in time. If you want
to restore to the most current time, you can skip this step.
Specify the location of all incremental back-up journal files. The files
should be listed in order of backup ID, if any.
Journal files that were backed up after a disk error occurred can be
included in the restoration process. They can also be applied after
all backed up journal files have been applied. (This may not be true
if the disks containing the journal files failed.)
After the restoration is complete, the database is in a consistent state
and has been shut down. Users may then start the database and begin
using it.
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