Migrating from the Metro Global Mirror session type to multi-target Metro Mirror – Global Mirror session type running in the cascading mode

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About this task

If you are running a Metro Global Mirror cascaded session or Metro Global Mirror with Practice session, you might want to migrate to a multi-target Metro Mirror – Global Mirror session or Metro Mirror – Global with Practice session.

The following are the advantages of migrating from a Metro Global Mirror or Metro Global Mirror with Practice session to a multi-target Metro Mirror – Global Mirror or multi-target Metro Mirror Global Mirror with Practice session type:

  1. The multi-target session types support DS8000 multi-target capabilities, simplifying some of the transitions between the sites.
    For example: : When the session is running H1->H2->H3 and a Recover H2 is issued, the cascaded Metro Global Mirror solution today copies data from H2->H3->H1 in order to get back to an H2->H1->H3 configuration. With the multi-target solution this is no longer necessary and the session can failback directly to a H2->H1->H3 configuration after the recover to H2.
  2. All the features of the Metro Global Mirror and Metro Global Mirror with Practice session are available in the multi-target session types.
    Note: Some transitions between sites are slightly different due to using the multi-target capabilities of the hardware.
  3. Starting from site three on the Metro Global Mirror session type requires a full copy. The new multi-target sessions use DS8000 multi-target technology to avoid full copies from site three.
    Note: The multi-target Metro Mirror – Global Mirror with Practice session still requires a full copy after starting at site three and the recovering back to either site 1 or site 2, for the replication back to site 3. This is because the volumes used in the practice session for the host at site 3 are different than the volumes used to replicate from site 1 or 2 to site 3. The Metro Mirror relationships does not require a full copy so there will still be Metro Mirror protection while the copy to site 3 occurs.

Procedure

  1. Ensure that the existing Metro Global Mirror or Metro Global Mirror with Practice session is in a Prepared and normal state before migrating session to the new multi-target session type.
    Important: Do not migrate the session when the session is not in a full three site configuration.
  2. Export all copy sets from the existing Metro Global Mirror or Metro Global Mirror with Practice session (Refer Exporting copy set data).
  3. Create a multi-target Metro Mirror – Global Mirror or multi-target Metro Mirror – Global Mirror with Practice session.
  4. Set the Consistency Group for all Global Mirror role pairs on the new session to match the consistency group number, used on the existing cascaded session.
  5. Import the copy sets from step 2 into the new multi-target session (Refer Importing copy set data).
  6. Remove all copy sets from the Metro Global Mirror or Metro Global Mirror with Practice session using the Keep existing relationships on the hardware option.
    Note: Make sure to use the Keep existing relationships on the hardware option or the procedure results in a full copy.
  7. Issue Start H1->H2->H3 from the new session to start the session in cascaded mode. This method assimilates the existing relationships on the hardware.
    Note: If the cascaded session was in H2->H1->H3 mode then you can issue the Set Production to Site 2 command followed by the Start H2->H1->H3 command.