IBM System storage DS6000 Series, Redbook

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Chapter 16. Metro Mirror examples
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Example 16-2 Resume suspended Metro Mirror pair from TSO
CESTPAIR DEVN(X'6400') PRIM(X'0002' AAVCA X'00' X'00') -
SEC(X'0003' AAVCA X'00' X'01') OPTION(SYNC) MODE(RESYNC)
ANTP8802I CESTPAIR DEVN(X'6400') PRIM(X'0002' AAVCA X'00' X'00')
SEC(X'0003' AAVCA X'00' X'01') OPTION(SYN
ANTP8802I (CONT) C) MODE(RESYNC)
ANTP0001I CESTPAIR COMMAND COMPLETED FOR DEVICE 6400. COMPLETION CODE:
00
IEA494I 6400,DS6400,PPRC PAIR PENDING,SSID=0002,CCA=00
IEA494I 6400,DS6400,PPRC PAIR FULL DUPLEX,SSID=0002,CCA=00
16.2 Failover and failback using TSO
In this example we perform a failover and a failback using TSO commands. These options
can be used in both planned and unplanned scenarios. We simulate a planned outage.
In this discussion, the volumes at the primary site are referred to as the A volumes, and the
volumes at the recovery site are referred to as the B volumes. FlashCopy volumes are
referred to as C volumes.
16.2.1 Failover process
The high level process for the failover in a planned scenario is as follows:
1. Quiesce applications at the primary site.
2. Issue the Metro Mirror CESTPAIR command to the secondary (B) volume as the DEVN,
specifying the ACTION(FAILOVER) 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.
3. If desired, FlashCopy the B volume suspended primaries to C volumes to provide safe
copies for interim disaster recovery protection.
4. Restart applications at the recovery site. This includes bringing the B volumes online.
Here we show examples of the TSO commands that can be used to accomplish these
actions.
CESTPAIR with FAILOVER
We use the CESTPAIR command with the ACTION(FAILOVER) to the B volume to reverse
the original Metro Mirror direction and start change recording as shown in Example 16-3.
Note that we have reversed the original PRIM and SEC parameters.
Example 16-3 Establish Metro Mirror pair using TSO
ANTP8802I CESTPAIR DEVN(X'6430') SEC(X'2060' AAGXA X'30' X'00')
PRIM(X'0003' AAVCA X'30' X'01') ACTION(FAILOVER)
ANTP0001I CESTPAIR COMMAND COMPLETED FOR DEVICE 6430. COMPLETION CODE:
00
Tip: You may want to do a FlashCopy of your recovery site prior to running the
resynchronization, because the resynchronization process does not apply the updated
tracks in the order they were updated, and therefore you will have a data consistency
exposure until the last volume pair is again in duplex state.