BEGIN BACKUP
Begins an
online backup.
SYNTAX
DESCRIPTION
The BEGIN
BACKUP command places a database in a special state that allows you to
back up all files without requiring other users to disconnect and without
shutting down the database. To execute the BEGIN BACKUP command, you must
have DBA or SYSADM security privileges.
Media failure
is the failure of the online secondary or auxiliary storage of a computer
system. The most common secondary and auxiliary storage devices are hard
disks. Media failures are usually caused by physical trauma to the disk
itself, such as: head crash, fire, earthquake, or exposure to vibration
or g-forces outside its physical operating limits.
When a media
failure occurs, one or more files can be physically damaged as a result
of the failure. There is nothing that can prevent the loss of data in
the damaged files, but the database can be successfully restored if the
database provides archiving or backup capability. This allows you to create
a backup of your database files at periodic intervals, which you can use
to restore the database in the event of a media failure. There are several
different types of backups, as explained below.
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. A DBMS must explicitly
provide the capability to back up a database online, since it is still
running and still has users connected.
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 before the shut
down. Offline backups can be inconvenient for users, since they must remember
to complete all active transactions and disconnect from the database.
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.
A full backup
is any backup that creates a copy of all data and journal files, providing
a copy of the entire database system at one point in time. Because full
backups archive the entire database, they require a large amount of storage
space, but you can restore the database fairly quickly.
An incremental
backup is any backup that creates a copy of only the journal files that
have changed since the last full backup. These files provide a copy of
the changes made to the database since the last full backup. Because incremental
backups archive only journal files, they require only a small amount of
storage space, but you need more time to restore the database.
DBMaker
supports four types of backups: offline full backups, online full backups,
online incremental backups, and online incremental to current backups.
Before you perform either type of incremental backup, you must perform
either an offline full backup or an online full backup. If you don't perform
a full backup first, you may be unable to restore your database in the
event of a media failure.
To perform
an offline full backup, you must make sure all users are disconnected
and shut down the database. If any errors occur while the database is
shutting down, you may be unable to complete the backup operation or restore
the database at a later time. Use operating system commands or backup
utilities to back up all data, BLOB, and journal files to the backup device.
Using an offline full backup, you can restore a database up to the point
in time it was shut down.
To perform
an online full backup, you can start the database in NON-BACKUP, BACKUP-DATA,
or BACKUP-DATA-AND-BLOB mode (see page 3-56 for more information on backup
modes). To begin the backup, you issue the BEGIN BACKUP command. Use operating
system commands or backup utilities to back up all data and BLOB files
to the backup device. After these files have been backed up, issue the
END BACKUP DATAFILE command. Then use operating system command or backup
utilities to back up all journal files. After these files have been backed
up, issue the END BACKUP JOURNAL command to complete the backup and return
the database to normal operation. Using an online full backup, you can
restore a database from the point in time the END BACKUP DATAFILE command
was executed to the point in time the currently active journal file was
copied.
To perform
an online incremental backup, you must start the database in either BACKUP-DATA
or BACKUP-DATA-AND-BLOB mode (see page 3-56 for more information on backup
modes). To begin the backup, you issue the BEGIN INCREMENTAL BACKUP command.
DBMaker will list all journal files you need to copy and a backup ID for
each file. In an online incremental backup, DBMaker will only back up
journal files that have been used since the last full online backup, excluding
the currently active journal file. Record the filename and backup ID of
each file in a safe location; these will be used if you restore you database.
Use operating system commands or backup utilities to back up the journal
files in the list to the backup device. After these journal files have
been backed up, issue the END BACKUP JOURNAL command to complete the backup
and return the database to normal operation. Using an online incremental
backup, you can restore a database from the point in time the END BACKUP
DATAFILE command was executed in the previous full backup, to the point
in time the last committed transaction was written to the last full journal
file.
To perform
an online incremental backup to current, the database must have been started
in BACKUP-DATA or BACKUP-DATA-AND-BLOB mode (see page 3-56 for more information
on backup modes) . To begin the backup, you issue the BEGIN INCREMENTAL
BACKUP TO CURRENT command. DBMaker will list all journal files you need
to copy and a backup ID for each file. In an online incremental backup
to current, DBMaker will back up all journal files that have been used
since the last full online backup, including the currently active journal
file. Record the filename and backup ID of each file in a safe location;
these will be used if you restore you database. Use operating system commands
or backup utilities to back up the journal files in the list to the backup
device. After these journal files have been backed up, issue the END BACKUP
JOURNAL command to complete the backup and return the database to normal
operation. Using an online incremental backup to current, you can restore
a database from the point in time the END BACKUP DATAFILE command was
executed in the previous full backup, to the point in time the currently
active journal file was copied.
Only users
that have read permission on the database files from the operating system
can perform an offline full backup, and only users with DBA or SYSADM
security privileges can perform online backups. In addition, only one
user at a time can perform an online backup.
You can abort an online backup at any time by issuing the ABORT BACKUP
command. (For more information, see the ABORT BACKUP command.) After this
command executes, you will not be able to use the files from this backup
to restore the database.
You can
perform a full online backup at any time with the database in any backup
mode, including NON-BACKUP mode. Incremental online backups may only be
performed when the database is running in BACKUP-DATA or BACKUP-DATA-AND-BLOB
mode.
Backup mode
indicates the type of information DBMaker will back up during an online
incremental backup. There are three backup modes: NON-BACKUP, BACKUP-DATA,
and BACKUP-DATA-AND-BLOB. You can change the backup mode online or offline,
using one of three different methods: offline with the DB_BMODE keyword
in the dmconfig.ini configuration file, online with the iSQL SET command
at the dmSQL command prompt, or online with the Server Manager utility
provided with DBMaker.
NON-BACKUP
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.
To set the
backup mode to NON-BACKUP using the DB_BMODE keyword, open the dmconfig.ini
configuration file using any text editor and change the value of DB_BMODE
to 0. You may use the SET BACKUP OFF command during an online full backup
to set the backup mode to NON-BACKUP. This command must be executed after
the BEGIN BACKUP command, but before the END BACKUP JOURNAL command, and
only during an online full backup.
BACKUP-DATA
mode provides protection for data (excluding BLOB data) that was added
or changed since the last full backup; BLOB data is not recorded in the
journal. In this mode, DBMaker can perform an online incremental backup,
but since changes to BLOB data are not recorded in the journal, they are
not stored in the backup journal files. Any records containing BLOB data
that have been added or changed since the last full backup will have the
BLOB data replaced with a NULL value. After restoring the database, you
must manually update all of these records with the new BLOB data. 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.
To set the
backup mode to BACKUP-DATA using the DB_BMODE keyword, open the dmconfig.ini
configuration file using any text editor and change the value of DB_BMODE
to 1. You may use the SET DATA BACKUP ON command during an online full
backup to set the backup mode to BACKUP-DATA. This command must be executed
after the BEGIN BACKUP command, but before the END BACKUP JOURNAL command,
and only during an online full backup.
BACKUP-DATA-AND-BLOB
mode provides protection for all data (including BLOB data) that was inserted
or updated since the last full backup; BLOB data is included in the journal.
In this mode, DBMaker can perform an online incremental backup, and all
data will be stored in the backup journal files. A database can use the
journal to fully recover from instance failure, and can 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.
To set the
backup mode to BACKUP-DATA-AND-BLOB using the DB_BMODE keyword, open the
dmconfig.ini configuration file using any text editor and change the value
of DB_BMODE to 2. You may use the SET BLOB BACKUP ON command during an
online full backup to set the backup mode to BACKUP-DATA-AND-BLOB. This
command must be executed after the BEGIN BACKUP command, but before the
END BACKUP JOURNAL command, and only during an online full backup.
EXAMPLES
The following
example shows the steps involved in a full online backup. To begin, you
issue the BEGIN BACKUP command to notify DBMaker that a full backup is
in progress. Then use operating system commands to copy all data and BLOB
files to the backup location. Once the files are copied, you issue the
END BACKUP DATAFILE command. Then use operating system commands to copy
all journal files to the backup location. Once the files are copied, you
issue the END BACKUP JOURNAL command. Following this command, the database
returns to normal operation.
BEGIN BACKUP
Copy data and BLOB files to backup location using OS commands
Change backup mode if desired
Abort the backup if desired
END BACKUP DATAFILE
Copy journal files to backup location using OS commands
Change the backup mode if desired
Abort the backup if desired
END BACKUP JOURNAL
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The
following example shows the steps involved in an incremental online backup.
To begin, you issue the BEGIN INCREMENTAL BACKUP command to notify DBMaker
that an incremental backup is in progress. DBMaker will list all journal
files that you need to copy and a backup ID for each file. Use operating
system commands to copy these journal files to the backup location, and
record the backup ID for use during restoration. Once the files are copied,
you issue the END BACKUP JOURNAL command. Following this command, the
database returns to normal operation.
BEGIN INCREMENTAL BACKUP
Copy journal files to backup location using OS commands
Abort the backup if desired
END BACKUP JOURNAL
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The
following example shows the steps involved in an incremental online backup
that backs up everything to the point in time the currently active journal
file is copied. To begin, you issue the BEGIN INCREMENTAL BACKUP TO CURRENT
command to notify DBMaker that an incremental backup to current is in
progress. DBMaker will list all journal files that you need to copy and
a backup ID for each file. Use operating system commands to copy these
journal files to the backup location, and record the backup ID for use
during restoration. Once the files are copied, you issue the END BACKUP
JOURNAL command. Following this command, the database returns to normal
operation.
BEGIN INCREMENTAL BACKUP TO CURRENT
Copy journal files to backup location using OS commands
Abort the backup if desired
END BACKUP JOURNAL
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RELATED
COMMANDS
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