– Dynamic RAID Migration (DRM) to change the RAID level of an subsystem.
– Dynamic Segment Size (DSS) to change the segment size of a logical drive.
v You cannot start a rollback operation if the base logical drive is participating in a VolumeCopy.
v You cannot start a rollback operation if the base logical drive is a secondary logical drive in a remote
mirror. However, if the base logical drive is the primary logical drive in a remote mirror, you can start
a rollback operation. Additionally, you cannot perform a role reversal in a remote mirror if the primary
logical drive is participating in a rollback operation.
v A rollback operation fails if any of the used capacity in the associated Enhanced FlashCopy repository
logical drive has unreadable sectors.
Setting Enhanced FlashCopy Image Rollback Priority
Rollback operations require some level of system overhead, which can reduce overall system
performance. You can define the level of overhead the system devotes to a rollback operation using the
create EnhancedFlashCopyGroup command or the create consistencyGroup command. These commands
have a rollbackPriority parameter. Values for the rollbackPriority parameter range from highest
through lowest. The highest value means that the rollback operation has priority over all other host I/O.
The lowest value means that the rollback operation should be performed with minimal impact to host
I/O.
Starting an Enhanced FlashCopy Image Rollback
When you start an Enhanced FlashCopy image rollback, the contents of the base logical drive
immediately start to change to the contents of the Enhanced FlashCopy image. To start an Enhanced
FlashCopy image rollback use the start EnhancedFlashCopyImage rollback command or the start
cgEnhancedFlashCopyImagerollback command. These commands accepts the name of one or more
member logical drives. The start EnhancedFlashCopyImage rollback command works with specific
Enhanced FlashCopy images. The start cgEnhancedFlashCopyImagerollback command works with
specific member logical drives in the consistency group.
Stopping an Enhanced FlashCopy Image Rollback
Attention: Possible loss of data access – Stopping an Enhanced FlashCopy image rollback can leave the
base logical drive and the Enhanced FlashCopy image unusable.
Stopping an Enhanced FlashCopy image rollback leaves the base logical drive in an indeterminate state
with potentially invalid or inconsistent data that is typically unusable by a host system. The base logical
drive appears as failed in the storage management software. Stop an Enhanced FlashCopy image rollback
only in cases where recovery options exist for restoring the data in a base logical drive. If you must stop
an Enhanced FlashCopy image rollback use the stop EnhancedFlashCopyImage rollback command or the
stop cgEnhancedFlashCopyImage rollback command.
You can cancel an active rollback that is in progress (actively copying data), a pending rollback (in a
pending queue awaiting resources to start), or a rollback that has been paused due to an error.
After you cancel a rollback operation, you must take one of the following actions:
v Reinitialize the content of the base logical drive.
v Perform a new rollback operation to restore the base logical drive (using either the same Enhanced
FlashCopy image that was used in the Cancel Rollback operation or a different Enhanced FlashCopy
image to perform the new rollback operation).
Note: If the Enhanced FlashCopy group on which the Enhanced FlashCopy image resides has one or
more Enhanced FlashCopy images that have been automatically purged, the Enhanced FlashCopy image
used for the rollback operation might not be available for future rollbacks.
Chapter 6. Using the Enhanced FlashCopy Images Premium Feature 6-19
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