You can create Q subscriptions that specify what changes
to capture from either of two tables, what queues to use for exchanging
change messages, and how to process the messages. Changes to either
of the two tables replicate to the other table.
Before you begin
- Plan how you want to group replication queue maps and Q subscriptions.
- On the server that has the first copy of the table, create the
control tables for the Q Capture and Q Apply programs. The control
tables for the Q Capture and Q Apply programs that are on each individual
server must have the same schema.
- On the server that has the second copy of the table, create the
control tables for the Q Capture and Q Apply programs.
- Create the two replication queue maps that will transport data
between each server. You need one replication queue map for replicating
data from the first copy of the table to the second, and one for replicating
data from the second copy of the table back to the first. (You can
do this task before you create Q subscriptions or while you create
Q subscriptions.)
Restrictions
- Stored procedures cannot participate in bidirectional replication.
- Because before values of LOB columns are not replicated in bidirectional
replication, conflicts for LOB columns are not detected.
- Identity columns in target tables that are part of the Q subscription
must be defined as GENERATED BY DEFAULT.
- Q subscriptions for tables that
have referential integrity relationships with each other should be
created at the same time (in the same CREATE QSUB command when you
are using the ASNCLP command-line program or in the same session with
the Create Q Subscriptions wizard in the Replication
Center).
About this task
One
Q subscription is created to replicate transactions from the first
copy of the table to the second copy of the table, and another Q subscription
is created to replicate transactions from the second copy of the table
back to the first copy. When you create Q subscriptions for bidirectional
replication using the ASNCLP command-line program or the Replication
Center, the administration tool creates both Q subscriptions at one
time.
Procedure
To create Q subscriptions for bidirectional replication,
use one of the following methods:
| Method |
Description |
|---|
| ASNCLP command-line program |
Use the CREATE QSUB command for bidirectional replication.
For example, the following commands set the environment and create
two bidirectional Q subscriptions for the EMPLOYEE table at servers
SAMPLE and SAMPLE2:SET SUBGROUP "bidirgroup";
SET BIDI NODE 1 SERVER DBALIAS SAMPLE SCHEMA RED;
SET BIDI NODE 2 SERVER DBALIAS SAMPLE2 SCHEMA BLUE;
SET CONNECTION SOURCE SAMPLE.RED
TARGET "SAMPLE2".BLUE REPLQMAP
"SAMPLE_RED_TO_SAMPLE2_BLUE";
SET CONNECTION SOURCE SAMPLE2.BLUE
TARGET SAMPLE.RED REPLQMAP
"SAMPLE2_BLUE_TO_SAMPLE_RED";
SET TABLES (SAMPLE.RED.RED.EMPLOYEE);
CREATE QSUB SUBTYPE B
FROM NODE SAMPLE.RED SOURCE
ALL CHANGED ROWS Y HAS LOAD PHASE I
TARGET CONFLICT RULE C CONFLICT ACTION F
FROM NODE SAMPLE2.BLUE SOURCE
ALL CHANGED ROWS N HAS LOAD PHASE E
TARGET CONFLICT RULE C CONFLICT ACTION I;
The SET CONNECTION statements specify the two replication
queue maps that are used. The FROM NODE statements specify options
that are unique to each Q subscription.
|
| Replication Center |
Use the Create Q Subscriptions wizard. To open the wizard,
expand the appropriate Q Capture or Q Apply schema, right-click the Q
Subscriptions folder, and select Create. On
the Target Tables page, review the target object profile. Modify the
profile if necessary so that the target tables for the Q subscriptions
meet your needs.
The target object profile determines if an
existing target table is used or if a new one is created. The Replication
Center looks for an object that matches the naming scheme that is
defined in the profile. If a matching object does not exist, then
the object is created.
|
Q Replication and Event Publishing