In a PPRC-XD environment, data must be allowed to drain from the B volumes to the A volumes before the PPRC path is established from the recovery site to the primary site.
Figure 1. Failback in a PPRC-XD Environment
- Quiesce applications at the recovery site to reduce the risk of data loss.
- Use the PPRC Establish Paths command to provide a path for data flow from the recovery site to the primary site. Paths are required between all LSSs in which PPRC pairs reside.
- Issue the PPRC Establish Pair command to the B volume as the DEVN, specifying the FAILBACK ACTION and reversing the original PRIMARY and SECONDARY parameters. This copies any changes recorded on the B volumes back to the A volumes
- Withdraw the optional FlashCopy® relationship at the recovery site if no longer needed.
- Allow data to drain from B volumes to A volumes.
- Verify that paths are still established from the primary site to the recovery site. Issue PPRC Establish Paths command if necessary.
- Issue the PPRC Suspend command to the B volume as the DEVN, suspending the reversed pairs.
- Issue the PPRC Establish Pair command to the A volume as the DEVN, specifying the FAILOVER ACTION with the original PRIMARY and SECONDARY parameters. This reestablishes the A volumes as suspended primaries, begins change recording on the A volumes, and releases write inhibit on the A volumes.
- Restart applications at the primary site.
- Issue the PPRC Establish Pair command to the A volume as the DEVN, specifying the FAILBACK ACTION with the original PRIMARY and SECONDARY parameters. This resynchronizes the A and B volumes in the recovery configuration and restores the pairs to duplex-pending-XD state.