Computer Drive User Manual

Chapter 31. IBM TotalStorage Productivity Center for Replication 477
31.7 TPC for Replication session states
Again, a session contains a group of Copy Sets (that is, RMC (PPRC) volume pairs or
FlashCopy pairs) that belong to a certain application. You may also consider it a collection of
volumes that belong to a certain application or system with the requirement for consistency.
Such a session may be in one of the following states:
Defined
A session is defined and may already contain Copy Sets or have no Copy Sets assigned yet.
However, a defined session is not yet started.
Preparing
The session started already and is in the process of initializing, which may be, for example, in
case of a first full initial copy for a Metro Mirror. It may also just reinitialize, which, for
example, may be the case for a resynchronization of a previously suspended Metro Mirror.
Once the initialization is complete, the session state changes to
prepared.
Prepared
All volumes within the concerned session completed the initialization process.
Suspending
This is a transition state caused by either a suspend command or any other suspend trigger,
which may be an error in the storage subsystem or loss of connectivity between sites.
Eventually the process to suspend Copy Sets ends and copying has stopped, which is
indicated by a session state of
suspended.
Suspended
Replicating data from site 1 to site 2 has stopped. Application writes to concerned volumes in
site 1 can continue (FREEZE & GO). An additional recoverable flag indicates whether the
data is consistent and recoverable.
Recovering
A session is about to recover.
TargetAvailable
The recover command has completed and the target volumes are write enabled and available
for application I/Os. An additional recoverable flag indicates whether the data is consistent
and recoverable.
31.8 Volumes in a copy set
With TPC for Replication, the role of a volume within Copy Services has been renamed to be
more generic and also to include other storage subsystems such as SVC.
A Copy Set contains the volumes that are part of a Copy Services relationship. Metro Mirror
knows two volumes per Copy Set. Global Mirror requires three volumes per Copy Set.
FlashCopy again consists of two volumes per Copy Set.
Important: Do not manage Copy Service volume pairs that are already managed with
TPC for Replication with some other software.