Metro/Global Mirror planned site swap to intermediate

If a planned outage occurs, use the following process for failover and restore operations at the intermediate site:

1. At the local site, ensure that data consistency is achieved between the A and B volume pairs. This process will help coordinate the A volumes and B volumes consistency and allow consistent data to be copied to the remote site.

   You can use either one of the following methods to create data consistency:

   • Quiesce I/O processing to the A volumes at the local site.
   • Freeze write activity to the Metro Mirror primary volumes by performing the following steps:
     1. Freeze updates to the A volumes in Metro Mirror relationships across the affected LSSs. This ensures that the B volumes are consistent at the time of the freeze. (One command per storage unit or LSS is required.) As a result of the freeze action, the following actions are taken:
        • I/O processing to the Metro Mirror volume pairs is temporarily queued during the time when updates are frozen.
        • The volume pairs that are associated with the source and target LSSs are suspended. During this time, the storage unit collects data that is sent to the A Metro Mirror volumes.
        • The established paths between the logical subsystem (LSS) pairs are disabled.
     2. Resume operations following a freeze. This operation is also called a thaw operation and it allows I/O processing to resume for the specified volume pairs.
2. Issue a PPRC establish pair command with the failover, force, and cascade options. Specify the remote site secondary devices (C volumes) as the primaries and the local site Metro Mirror primary devices (A volumes) as the secondaries.
3. Issue CRECOVER or PRECOVER commands to the intermediate devices (B volumes), for the Metro Mirror relationships (A volumes to B volumes).
4. Resume host I/O at the intermediate site.
5. Issue PPRC establish pair commands with the failback and force options from the remote site to the local site (site C to site A).
6. Wait for the first pass copy to complete from the remote to the local site (site C to site A), and then start the incremental re-synchronous change recording mechanism on the site B to site C pairs, with NOCOPY specified in the INCRESYNC parameter.
7. Use the RESSION command to stop Global Mirror at the intermediate site.
8. Suspend the Global Copy pairs between the intermediate and remote sites (site B to site C pairs).
9. Wait for all data to drain from the remote site back to the local site (site C to site A). An alternate from doing queries to wait for all out of sync data to drain is to convert the site C to site A pairs to synchronous. When they become full duplex, all data has been copied.
10. Suspend the site C to site A PPRC pairs.
11. Issue CRECOVER or PRECOVER commands to the remote devices (C volumes) to the B to C volumes, for the suspended site C to site B relationships.
12. Issue PPRC establish pair commands with failover and cascading to reverse the direction of the site C to site A relationships. The command is issued to the A devices.
13. Issue PPRC establish pair commands with failback to the site A to site C relationships.
14. Establish Metro Mirror by using the incremental resync change recording that has been in process since the site has swapped to the intermediate site, with the force option, from the intermediate to the local site (issue PPRC establish pair commands with option SYNC, mode INCRES, and force from site B to site A).
15. Issue PPRC establish pair commands to the site B to site A relationships to start the incremental resync change recording (issue PPRC establish pair commands with mode NOCOPY and INCRESYNC(START))
16. Wait for the site B to site A relationships to become full duplex and the site A to site C relationships to complete their first pass copy.
17. Start the Global Mirror, running from the local to the remote site in order to update the aged consistency group at the remote site.

The following steps show how to transit back to the original configuration (from site A to B to C):

1. Quiesce all host I/O activity and suspend the site B to site A relationships.
2. Issue a PPRC establish pair command with the failover, force, and cascade options. Specify the remote site devices (C volumes) as the primaries and the intermediate site devices (B volumes) as the secondaries.
3. Issue CRECOVER or PRECOVER commands to the local devices (A volumes), for the site B to site A relationships.
4. Resume host I/O at the local site.
5. Issue PPRC establish pair commands with the failback and force options from the remote site to the intermediate site (site C to site B).
6. Wait for the first pass copy to complete from the remote to the intermediate site (site C to site B), then start the incremental resynchronous change recording mechanism on the site A to site C pairs, with NOCOPY specified in the INCRESYNC parameter.
7. Use the RSESSION command to stop Global Mirror at the local site.
8. Suspend the Global Copy pairs between the local and remote sites (site A to site C pairs)
9. Wait for all data to drain from the remote site back to the local site (site C to site B). An alternate from doing queries to wait for all out of sync data to drain is to convert the site C to site B pairs to synchronous. When they become full duplex, all data has been copied.
10. Issue CRECOVER or PRECOVER commands to the remote devices (C volumes), for the suspended site C to site A relationships.
11. Suspend the site C to site B PPRC pairs.
12. Issue PPRC establish pair commands with failover and cascading to reverse the direction of the site C to site B relationships. The command is issued to the B devices.
13. Issue PPRC establish pair commands with failback to the site B to site C relationships.
14. Establish Metro Mirror by using the incremental resync change recording that has been in process since the site swap to the local site, with the force option, from the local site to the intermediate site (issue PPRC establish pair commands with option SYNC, mode INCRES, and force from A to B).
15. Issue PPRC establish pair commands to the site A to site B relationships to start the incremental resync change recording (issue PPRC establish pair commands with mode NOCOPY and INCRESYNC(START)).
16. Wait for the site A to site B relationships to become full duplex and the site B to site C relationships to complete their first pass copy.
17. Start the Global Mirror, running from the intermediate to the remote site in order to update the aged consistency group at the remote site.

You have changed the Metro/Global Mirror operations running from site A to B to C.