Operating System Software Owner manual

For more information on volume group modes, see “Volume Group Modes” (page 194).
Write Errors and Synchronous Volume Groups
For synchronous volume groups, when a write error occurs on the backup system:
• The host I/O completes without error.
• Remote Copy stops replication for the volume group.
• Remote Copy creates snapshots of each virtual volume in the volume group.
• Remote Copy generates an alert indicating that an I/O error has occurred on the backup
system and specifying the volume group that is stopped as a result.
• The offset and length of the I/O fails to complete on the secondary virtual volumes because
the link failures were recorded in the nonvolatile memory.
The system records failed I/O replication separately because Remote Copy creates the
snapshots of the primary virtual volumes on the primary system after I/O is written to the
primary virtual volumes, but before Remote Copy can write the I/O to the secondary virtual
volumes.
Restarting Synchronous Volume Groups after Write Errors
• Remote Copy does not automatically restart replication that was stopped as a result of write
errors. Even if the auto_recover policy is set, it only automatically restarts replication that
stopped as a result of link failure.
• To restart a synchronous volume group that stopped after a write error, issue the
startrcopygroup command on the primary system.
Read Errors
Read Errors during Initial Synchronization
During the initial synchronization process, Remote Copy:
• for synchronous volume groups: reads the base volume
• for asynchronous periodic volume groups: creates a read-only snapshot of the base volume
If the read request fails for any reason, Remote Copy:
• cancels the synchronization process
• marks the secondary volume as NotSynced
• issues an alert indicating that the synchronization failed
• does not stop replication
To synchronize the virtual volumes (in both synchronous and asynchronous periodic volume groups),
issue the syncrcopy command
Read Errors during Synchronization after Restart of Synchronous Volume Groups
Remote Copy automatically starts a resynchronization if a synchronous volume group is:
• fully synced
• stopped and then restarted
During resynchronization, Remote Copy compares the snapshot taken when the primary volume
group was stopped and the base volume and reads any new data from the snapshot. If the read
is successful, Remote Copy sends the new data to the secondary volume group.
210 Error Handling