IBM System storage DS6000 Series, Redbook

Page: 311 / 578

Chapter 23. Global Mirror options and configuration
287
If you see a situation other than the above four situations, then the Global Mirror mechanism
has been corrupted.
Case 1: FlashCopies still committed
This indicates the situation where all FlashCopy operations have completed their task (and
the next FlashCopy operations have not been started). In this situation, we don’t need any
action to correct the FlashCopy status because we have consistent data in all C volumes.
This state is also reached after the FlashCopies are complete, and Global Mirror is waiting to
create the next Consistency Group.
Case 2: FlashCopies partially issued
In this case, there is a group of FlashCopy pairs that are all
revertible
and another group of
FlashCopy pairs that are all
non-revertible
. Consistency can be restored if these two criteria
are true:
򐂰 The FlashCopy sequence number for all revertible pairs is equal.
򐂰 The FlashCopy sequence number for all non-revertible pairs is also equal.
This indicates that the FlashCopy operations were interrupted. Some FlashCopy operations
for the new consistency group were started, but not all of them.
The FlashCopy relationships that have not started are in a non-revertible state and all of them
have the same FlashCopy sequence number. Other FlashCopy relationships that had already
started are in a revertible state and all of them have the same FlashCopy sequence number,
but the number is different from the sequence number of the non-revertible FlashCopy
relationships.
Case 2 SOME - Some
FlashCopy pairs are
revertible and others
are not revertible. Revertible FlashCopy
pairs’ sequence
numbers are equal.
And non-revertible
FlashCopy pairs
sequence numbers
are equal, but do not
match the revertible
FlashCopies
sequence number.
revert
FC relations. Some FlashCopy
pairs are running in a
Consistency Group
process and some
have not yet started
their incremental
process.
Case 3 YES. YES.
revert
to all FC
relations.
All FlashCopy pairs
are in a new
Consistency Group
process and none
have finished their
incremental process.
Case 4 SOME - Some
FlashCopy pairs are
revertible and others
are not revertible. YES.
commit
FC relations. Some FlashCopy
pairs are running in a
Consistency Group
process and some
have already finished
their incremental
process.
Are all FC
relationships
revertible? Are all FC sequence
numbers equal? Action to take Comments