Moving a Global Mirror session to the recovery site in an unplanned outage

In step 4 of the following scenario, column header names and data values are cited that appear only in formatted output from the RQUERY command. You may prefer unformatted DSECT output from RQUERY. The values from formatted output are used here only as examples.

Figure 1. Moving Global Mirror Session to Recovery Site in an Unplanned Outage
Failover in a Global Mirror Environment. The steps describe commands to be issued at the primary site and at the recovery site.
  1. Issue the RSESSION command with the STOP ACTION and MASTER YES parameters specified. If the master storage control is unable to complete consistency group formation, if possible reissue RSESSION STOP specifying MASTER YES and the FORCE parameter.
  2. If the storage control subordinates have not stopped, issue the RSESSION STOP command, specifying NO for the MASTER parameter.
  3. Issue the PPRC Establish Pair command to the B volume as the DEVN, specifying FAILOVER for ACTION and reversing the original PRIMARY and SECONDARY parameters. This establishes the B volumes as suspended primaries, activates change recording on the B volumes, and releases write inhibit on the B volumes.
  4. Issue the RQUERY command to each of the suspended primary (B) volumes at the recovery site. Note the revertible status (column headed RvrtStat) and the FlashCopy® sequence numbers (column headed FCSeqNbr) in order to determine which step to perform next.
    • If all the FlashCopy relationships are non-revertible AND the FlashCopy sequence numbers of the relations are equal (RvrtStat = AllNRv&Eq), then the consistency groups on the C volumes are intact. Proceed to step 5.
    • If all the FlashCopy relationships are revertible AND the FlashCopy sequence numbers of the relations are equal (RvrtStat = AllRv&Eq), then you must issue the FlashCopy WITHDRAW command specifying the REVERT ACTION to all FlashCopy relationships in the consistency group. This restores the relationships to their prior state, resets the revertible state, and removes write inhibit on the B volumes. When the FlashCopy WITHDRAW command completes, proceed to step 5.
    • If the FlashCopy sequence numbers of the relationships are equal AND at least one of the relationships is in a non-revertible state (RvrtStat = Rv|NRv&Eq), then you must issue a FlashCopy WITHDRAW specifying COMMIT to all of the FlashCopy relationships in the consistency group. This commits the FlashCopy relationships to the current state, resets the revertible state, and removes write inhibit on the B volumes. When the FlashCopy WITHDRAW command completes, proceed to step 5.
    • If more than two non-zero FlashCopy sequence numbers are present, then the consistency groups have been corrupted and the recovery program cannot continue.
  5. Issue the FlashCopy Establish command specifying the C volumes as source and the B volumes as target, and specifying the FRR parameter. The B volumes are now consistent and the C volumes are no longer usable.
  6. When the FlashCopy FRR command completes, issue another FlashCopy Establish command establishing the B volumes as source and the C as target in a new relationship to create a backup copy.
  7. If desired, make a backup of the C volumes on tape for a safe copy.
  8. Restart applications at the recovery site.

    If the primary site is operational, the Global Mirror session can be reversed with the following steps.

  9. 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.
  10. Issue the CESTPAIR command specifying the B volume as the DEVN with the FAILBACK ACTION, again reversing the original PRIMARY and SECONDARY parameters. This copies any changes from the B volumes to the A volumes.
  11. Use the FlashCopy Withdraw command to end the FlashCopy relationship at the recovery site.
  12. Start a new FlashCopy relationship between A and C′ volumes at the primary site, using the FlashCopy Establish command and specifying ASYNC with the MODE parameter.
  13. Issue the RSESSION DEFINE command at the recovery site to specify the topology of the new Global Mirror session.
  14. Use the PPRC Establish Paths command to provide a path for data flow between the Master and storage control subordinates at the recovery site.
  15. Issue the RVOLUME command specifying the JOIN ACTION to populate the session with primary volumes at the recovery site.
  16. Issue the RSESSION command to the Master at the recovery site, specifying the START ACTION to begin the Global Mirror session.
Parent topic: Failover/failback for a Global Mirror session