You designate a preferred
replay member by issuing the START HADR command
on that member. If you want to change that designation, you have to
reissue the command.
Note that if a database is already
active and in the desired role, the START HADR command
will be a nop (no operation performed) that returns an error, and
the preferred replay member is not updated. Use the following procedure
to designate or redesignate the preferred replay member.
About this task
The preferred replay member is the member that is preferred
for replaying logs on an HADR standby database in a DB2® pureScale® environment.
On a standby, it still might not be the member doing the actual replay.
On the primary, it is the first member that the standby replay service
attempts to start on if that primary becomes the standby. The preferred
replay member designation is persistent and can only be changed by
starting and stopping HADR.
Procedure
To designate a preferred replay member
- On the standby:
- Issue the DEACTIVATE DATABASE command from
any member in the standby cluster.
- Issue the START HADR command with the AS
STANDBY option on the member that you want to designate as
the preferred replay member.
- On the primary:
- Issue the STOP HADR command from any member
in the primary cluster.
Note: The primary remains active during this
procedure.
- Issue the START HADR command with the AS
PRIMARY option on the member that you want to designate as
the preferred replay member.
Note: This designation only takes effect
if the primary database switches to the standby role.
Results
If the START HADR command
completes successfully, the preferred replay member is updated. If
the START HADR command fails, the preferred member
might or might not have been updated, depending on how far the command
execution went. To ensure that the designation applies to the correct
member, rerun the procedure described in this task.