CREATE REPLICATION
Creates
a new synchronous table replication for a table.
SYNTAX
| replication_name |
Name
of the synchronous table replicaton you want to create. |
| local_table_name |
Name
of the local table you want to replicate. |
| column_name |
1. Name
of a column in the local table you want to replicate.
2. Name of a column in the remote table you want to replicate to. |
| search_condition |
Conditions
a row must meet to be replicated. |
| remote_table_name |
Name
of the table in the remote database you want to replicate to. |
DESCRIPTION
The CREATE
REPLICATION command creates a new synchronous table replication for a
table. You cannot create a replication on a temporary table, a synonym,
or a view. To execute the CREATE REPLICATION command on a table you must
be the table owner, or have DBA or SYSADM security privileges.
A table
replication creates a full or partial copy of a table in a remote location.
This allows users in remote locations to work with a local copy of data.
The local copy remains synchronized with the databases in other locations.
This way each database can service data requests immediately and efficiently,
without having to go to another machine over a slower network connection.
This is not the same as backing up the database to a remote location,
since the synchronization is done on a transaction-by-transaction basis
by the DBMS itself, without any intervention from users.
There are
two primary types of table replication: synchronous and asynchronous.
Synchronous table replication modifies the remote table at the same time
it modifies the local table, while asynchronous table replication stores
changes to the local table and modifies the remote table based on a schedule.
The CREATE REPLICATE command creates a synchronous table replication.
Synchronous
table replication in DBMaker uses a global transaction model, in which
the replication of data to the remote table is treated as an integral
part of the local transaction. (A transaction is traditionally defined
as a logical unit of work, or one or more operations on a database that
must be completed together to leave the database in a consistent state.
Transactions are self-contained an must either complete and change the
data, or fail and leave the data unchanged.) This means that if the replication
of data to the remote database fails, the transaction on the local table
will also fail.
When you
modify a synchronous table replication you must specify the replication
name, the local table name, and the names of the additional remote tables
you want to replicate to. Both the local table and the remote tables must
already exist in their respective databases. DBMaker will automatically
drop any replications you create on a table when you drop the table.
DBMaker
will replicate the entire table unless you specify the individual columns
you want to replicate using a column list. When you replicate an entire
table without providing a column list, the columns in the local table
and corresponding columns in the remote table must have the same name
and data type. If the column names in the local and remote tables are
different, you can provide a column list for the remote table. Columns
in the local table (from left to right) will replicate to the corresponding
columns named in the column list for the remote table. You can explicitly
specify which columns in the local table correspond to columns in the
remote table by providing a column list for both the local and remote
tables. In all cases, you must include the primary key columns in the
replication, and the number and data type of primary key columns in both
tables must match.
Unlike most
database objects, DBMaker does not identify replications using fully qualified
names (a combination of owner and object names), but associates them with
tables instead. For this reason all replication names on the same table
must be unique. The replication operates with the same security and object
privileges as the owner of the trigger table, unless the remote table
is specified using links. In this case, the replication operates with
the same security and object privileges as the link.
The WHERE
keyword is optional. This keyword specifies the search condition to uses
when replicating data to a remote table. DBMaker will only replicate rows
that satisfy the search condition. See the WHERE clause in the description
of the SELECT command for more information.
The CLEAR
DATA/FLUSH DATA/CLEAR AND FLUSH DATA keywords are optional. These keywords
specify the operations that will take place when you create a replication.
The CLEAR DATA keywords will delete all data from the remote table when
you create the replication. The FLUSH DATA keywords will copy all data
that matches a search condition into the remote table. The CLEAR AND FLUSH
DATA keywords will clear all data from the remote table, and then copy
all data that matches a search condition into the remote table. If you
do not specify an action, no action will take place.
Replication
names have a maximum length of eighteen characters, and may contain numbers,
letters, the underscore character, and the symbols $ and #. The first
character may not be a number.
EXAMPLES
The following
example creates a replication named EmpRep for the local table named Employees.
The remote database is identified by a database configuration section
named FieldOffice in the local dmconfig.ini configuration file. The remote
table is also named Employees, and all column names and data types in
both tables are the same.
CREATE REPLICATION EmpRep WITH PRIMARY AS Employees
REPLICATE TO FieldOffice:Employees
|
The following
example is similar to the above example, but all data in the remote table
is deleted and then any existing data in the local table is sent to the
remote table.
CREATE REPLICATION EmpRep WITH PRIMARY AS Employees
REPLICATE TO FieldOffice:Employees
CLEAR AND FLUSH DATA
|
RELATED COMMANDS
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