IBM System Storage DS3000, Programming Manual

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v
You can run the command to change roles from either primary or secondary storage subsystem.
v
All of the mirror pairs of the Enhanced Global Mirror Group must have a valid recovery point before
performing a role reversal.
v
The Enhanced Global Mirror Group must be in a non-failed state and must not already be in role
changing operation.
v
You cannot change roles if the Enhanced Global Mirror Group contains incomplete or orphaned
member logical drives.
When the communication between the Enhanced Global Mirroring storage subsystems is operating
normally, role reversal is coordinated between the local and remote storage subsystems. During role
reversal these two events occur:
v
The original primary logical drives are protected from new write requests just as if they were
secondary logical drives.
v
A resynchronization process from the original primary logical drives to the original secondary logical
drives starts.
The resynchronization operation completes after all mirror-pairs of the Enhanced Global Mirror Group
are fully synchronized. If a scheduled synchronization operation is in progress when a controller receives
the role change request, the resynchronization operation is stopped and restarted. This results in all
regions flagged in both the host-write tracking delta log and the synchronization delta log being copied
to the secondary logical drives.
After the synchronization finishes and the roles are changed these actions take place:
v
Recovery points are created on the original primary storage subsystem that is now the secondary
storage subsystem.
v
The logical drives on the new primary storage subsystem change state to Optimal and operate
normally: servicing read and write requests, tracking write requests, and periodically synchronizing to
the secondary logical drives.
To change roles, use this form of the
set enhancedGlobalMirrorGroup
command
set enhancedGlobalMirrorGroup ["enhancedGlobalMirrorGroupName"] role=(primary | secondary)
The
role
parameter enables you to define the role you want from either the primary storage subsystem
or the secondary storage subsystem. For example, if you are on the primary storage subsystem and you
want to change roles, use the
secondary
parameter. The command would look like this:
set enhancedGlobalMirrorGroup ["enhancedGlobalMirrorGroupName"] role=secondary
As soon as you run this command, the storage subsystems start changing roles.
Two optional parameters support changing the roles of the primary storage subsystem and the secondary
storage subsystem:
v force
v nosync
The force parameter forces a role change if the communications link between the storage subsystems is
down and promotion or demotion on the local side results in a dual-primary condition or a
dual-secondary condition. To force a role reversal, set this parameter to
TRUE
. The default value is
FALSE
.
The
nosync
parameter defines whether to perform an initial synchronization between the primary storage
subsystem and the secondary storage subsystem before a role reversal operation is performed. To perform
an initial synchronization, set this parameter to
TRUE
. The default value is
FALSE
.
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IBM System Storage DS3000, DS4000, and DS5000: Command Line Interface and Script Commands Programming Guide