Setting up incremental resync for Metro/Global Mirror

The Incremental Resync for Metro/Global Mirror change recording mechanism can be started in the following conditions:

When a Peer-to-Peer Remote Copy (PPRC) pair is established.
A subsequent Establish PPRC command (by TSO or API) with the appropriate keyword is issued on an already established pair.
To start the Incremental Resync, specify the INCRESYNC(START) when you use the CESTPAIR command to specify PPRC primary and secondary volumes. See CESTPAIR – establishing volume pairs for details.

The incremental Resync for Metro/Global Mirror stops changing recording in the following conditions:

The establish PPRC command with INCRESYNC(STOP) is issued.
The PPRC pair is deleted.

Note:

If the establish PPRC command is issued and results in more than two secondaries for the specified PPRC primary, the command is rejected.
If an establish PPRC command with the start incremental resync keyword is issued to an already established PPRC pair that has the incremental resync change recording mechanism already started, the command is accepted and no action is taken.
If an establish PPRC command with the stop incremental resync keyword is issued to an already established PPRC pair that does not have the incremental resync change recording mechanism already started, the command is accepted and no action is taken.

If the intermediate site is lost, you can continue your operations by issuing an Establish PPRC command with Incremental Resync mode specified to connect the local volume to the remote volume. To retain consistency over distance, the pairs are established as Global Copy (extended distance, or MODE(XD)) and the Global Mirror environment created at the local site (define session to LSS’es involved, add volumes to session, and start session at the local site).

Note:

If this Establish PPRC command for recovery is issued and the Incremental Resync change recording mechanism does not run, the command is rejected.
If this Establish PPRC command for recovery is issued and specified primary volume is not a primary volume whose secondary is the primary for the specified secondary volume, and FORCE is not specified, the command is to be rejected.

With the incremental resync support installed, if there is an intermediate site failure, the procedure to restart the recovery environment running Global Mirror from the local site to the remote site is simplified, and a full copy is not required.