Considerations after HADR role switch

In a high availability disaster recovery (HADR) environment, users must consider what happens in the event of an HADR role switch.

Quiesced table spaces

In an HADR environment, a table space quiesce is not preserved during a role switch.

When a table space is quiesced on the primary database, no log records are generated, so there is no effect on the standby database. If the standby has to take over as the primary before the quiesce has been released, that table space will be fully available on the new primary. You should be aware that if you continue the job that required the table space to be quiesced on the original primary, then on the new primary, the job is no longer protected by the quiesce

If there was a role switch (that is, if the old primary is now the new standby), changes to the table space on the new primary are replayed on the new standby. However, if the primary role is failed back to the old primary, the quiesce state will still be in effect for that table space.

Event monitor state

In an HADR environment, the event monitor state is not preserved during a role switch, but an autostart event monitor will be started automatically on the new primary database after a role switch.

When a non-autostart event monitor is manually started on the primary database, no log records are generated, so there is no effect on the standby database. If the standby database has to take over as the primary, the non-autostart event monitor will not be started on the new primary database. When an autostart event monitor is manually stopped on the primary database, it also has no effect on the standby database. If the standby takes over as the primary, the autostart event monitor will be started on the new primary database.

Users should be aware that if the state of an event monitor on the primary database is changed, the state may not be the same on the new primary database after a role switch. It would be a best practice to use the autostart event monitor to ensure no loss of event monitor data.