Chapter 2: Failover and Failback

Performing failback

Failback is accomplished in four steps:

Prepare for failback.

IBM HACMP for AIX automatically fails back when the primary node is ready to resume normal companion mode. See Chapter 8, “Configuring Adaptive Server for Failover on IBM AIX,” for more information.

Issue prepare_failback from the secondary companion to release database devices and databases.
```
sp_companion server_name ‘prepare_failback’
```
where server_name is the name of the secondary companion. The secondary companion issues messages similar to the following during a failback:
```
Step:Access across the servers verified
Step:Primary databases are shutdown in secondary
Step:Primary databases dropped from current secondary
Step:Primary devices released from current secondary
Step:Prepare failback for primary server  complete
(return status = 0)
```
Move the devices back to the primary node according to individual platform subsystem.
The high availability system restarts the primary companion automatically.
Run sp_companion with the do_advisory option to make sure there are no attribute settings to prevent a failback from succeeding. See Chapter 6, “Running do_advisory.”
After fail back is complete, issue sp_companion from the primary companion (the companion that originally failed) to return to normal companion mode. See the appropriate platform-specific chapter for more information about sp_companion resume

You cannot connect clients with the failover property until you issue sp_companion resume. If you try to reconnect them after issuing sp_companion prepare_failback, the client hangs until you issue sp_companion resume.

Cluster locks in a high availability node

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