IBM XIV Storage System Copy Services and Migration

After this changeover, the following is true:► The slave volume or consistency group is now the master.► The last_replicated snapshot is restored to the volumes► The coupling has the status of inactive (Figure 6-24).Figure 6-24 Slave becomes master►The coupling remains in inactive mode (Figure 6-25). This means that remote mirroring isdeactivated. This ensures an orderly activation when the role of the peer on the other siteis changed.Figure 6-25 Original master becomes inactiveThe new master volume or consistency group starts to accept write commands from localhosts. Because coupling is not active, in the same way as for any master volume, a log ismaintained of which write operations must be sent to the slave volume when communicationresumes.After changing the slave to the master, an administrator also must change the original masterto the slave role before communication resumes (Figure 6-26). If both peers are left in thesame role (master), mirroring cannot be restarted.Figure 6-26 Change role of a master consistency groupChapter 6. Asynchronous Remote Mirroring 167