Working with user-defined consistency groups

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A consistency group is a set of target volumes that are updated to preserve write order, and are therefore recoverable. You can define the name of a consistency group and use that name to assign multiple Global Mirror or Metro Global Mirror sessions to the same consistency group.

About this task

For Global Mirror role pairs on Copy Services Manager sessions with DS8000® volumes, you can define a 2-digit hex number that represents the Global Mirror session ID used on the DS8000 storage system. You can use this ID for the following reasons:
  • To ensure that a Copy Services Manager session uses only the specified session ID, when it is managing a Global Mirror session on a DS8000 storage system. If not specified, Copy Services Manager automatically picks a session ID that is not currently in use.

  • To assign multiple Global Mirror role pairs in separate sessions to use the same DS8000 session ID. DS8000 allows only a single session ID per logical subsystem (LSS). By setting the same session ID on multiple Copy Services Manager sessions that use the same DS8000 storage system, you can manage each Copy Services Manager session separately (suspend and recover each individually). You can also go beyond the hardware limits on the number of Global Mirror sessions that DS8000 can manage.

    When a Suspend command is issued to a session that is sharing the consistency group ID, Copy Services Manager suspends the volumes in that session but automatically restarts any other sessions that use the same session ID. If you want to suspend all the sessions with the Suspend command, specify the following property in the server properties:

    csm.server.suspend_all_shared_gm_sessions=true
    Note: For more information, see rmserver.properties file.
    Note: When using the same consistency group for "Practice" sessions, the Flash command does a Pause of the consistency group under the covers in order to create a consistent point in time of the data at the remote site. This means any other sessions that share the same consistency group would be temporarily suspended as it is with the Suspend command, but then automatically restarted.
For Metro Mirror role pairs on Copy Services Manager session with DS8000 volumes, you can define a consistency group name of up to 12 alphanumeric characters. You can use the consistency group name for the following reasons:
  • When multiple sessions with HyperSwap or Hardened Freeze configurations, have the same user-defined consistency group name on a role pair, and the sessions are associated to the same z/OS Sysplex, Copy Services Manager loads the HyperSwap or Hardened Freeze configuration onto the Sysplex. Copy Services Manager uses all the volumes across all sessions that share user-defined consistency group name. You can manage HyperSwap across multiple replication configurations that include Metro Mirror and Metro Global Mirror.
  • For sessions that do not have HyperSwap or Hardened Freeze that is enabled, the user-defined consistency group name can be used to ensure Metro Mirror consistency across multiple sessions. When a planned or unplanned freeze occurs, Copy Services Manager issues a hardware freeze command across all sessions that have the same user-defined consistency group name. The Release I/O command is issued after the hardware freeze command has been issued.

Procedure

Follow these steps to assign a new user-defined consistency group name for one or more Global Mirror or Metro Global Mirror sessions:

  1. In the menu bar, click Sessions.
  2. On the Sessions page, select one or more sessions.
  3. From the Session Actions list, select View/Modify > Set Consistency Group Name.
  4. In the Set Consistency Group Name window, enter the new consistency group name that you want to assign to each role pair.
  5. Click OK.