Discarding changes or committing changes to consistency groups

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Use this process to determine whether to discard or commit changes to FlashCopy volumes that are part of consistency groups.

About this task

When you query the state of the consistency group, the output displays whether the sequence numbers are equal for all FlashCopy relationships that are part of the consistency groups and whether the FlashCopy relationships are revertible.

If the sequence numbers are not equal, which results from something going wrong during a FlashCopy consistency group formation operation, you must determine the action to take. The action that you take depends on which phase the consistency group formation was in at the time of the failure. For example, if the failure occurred while FlashCopy commands were processing, intervention is required to provide the consistency. The action depends on the current status of the FlashCopy, where the sequence numbers and the revertible state are important.

The following options are available to help you determine the action to take:

Procedure

  • Discard changes (revert to a previous consistent state).
    Assume that the sequence numbers of the FlashCopy relationships are different and the copy process has not started for all the volumes. In this case, the FlashCopy data is inconsistent and cannot be used. You must revert changes, which removes all not-committed data from the FlashCopy target and reverts (or is restored) to the last consistency group.
    Note: You can discard changes to FlashCopy target volumes only if you have modified the FlashCopy relationship using the setflashrevertible command, which changes the Revertible value to Enabled.

    When you revert a FlashCopy relationship that is in a revertible state, ensure that you specify its associated FlashCopy sequence number.

  • Commit all FlashCopy relationships in the consistency group to the current level.

    Assume that the sequence numbers are all equal and there is a mix of revertible and nonrevertible volumes and the copy process to the FlashCopy target volumes has occurred but not completed for some volumes. In this case, the FlashCopy target volumes are usable and the process has to be committed manually.

    This is done by issuing a commit command to all revertible FlashCopy relationships to commit data to the FlashCopy target volumes and create data consistency between the source and target volumes. The commit process specifies that the last consistency group that has been created by the Global Mirror session is committed to the current state, and reverting to the previous consistency group state is no longer possible.
    Note: You can commit changes to FlashCopy target volumes only if you have modified the FlashCopy relationship using the setflashrevertible command, which changes the Revertible value to Enabled.