Hitachi TrueCopy for IBM z/OS User and Reference Guide (T5211-96001, June 2007)

6-28 Performing TrueCopy for z/OS Pair Operations
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Releasing TrueCopy for z/OS Pairs
A TrueCopy for z/OS pair should be released from the MCU only when it is no
longer necessary to maintain a remote copy of the M-VOL. When a TCz pair is
released from the MCU, the MCU stops all TCz copy operations for that pair
and changes the pair status of the M-VOL and R-VOL to simplex. After a pair is
released, the MCU continues to accept all subsequent write I/O operations to
the M-VOL and will not keep track of the M-VOL updates.
A TCz pair should be released from the RCU only if you need to access the R-
VOL, for example, to perform ICKDSF on the R-VOL or for disaster recovery.
When a TCz pair is released from the RCU, the RCU changes the R-VOL pair
status to simplex but does not change the pair status of the corresponding M-
VOL. When the MCU performs the next TCz operation, the MCU detects that
the R-VOL status changed and changes the status of the M-VOL to suspended-
delete pair to RCU. When you release a pair from the RCU in order to access
the R-VOL, remember that the R-VOL and M-VOL have the same VOLSER, and
take appropriate precautions to prevent a system problem due to duplicate
VOLSERs. To restart a pair which was released from the RCU, you must first
release the pair from the MCU, and then add the pair from the MCU using the
appropriate initial copy option (Entire Volume or None) to restart the pair.
You can release all TCz Synchronous pairs between an MCU and RCU (same
CU). You can also release all TCzA pairs in a consistency group by connecting
to the MCU. The TCzA pair status will change to deleting when the delete
operation is accepted by the MCU and RCU, and then to simplex after the
internal release pair process is complete. In addition, you can release TCzA
pairs according to their consistency status (e.g., for disaster recovery) by
connecting to the RCU (the RCU maintains the consistency status).
Note: The CDELPAIR TSO command can be used to release TCz pairs and
TCzA groups of pairs from the MCU.
WARNING: Please see the warning about duplicate VOLSERs.
WARNING: As a general rule, when you want to release a TrueCopy for z/OS
Async pair from the MCU, it is strongly recommended that you perform the
release pair operation after the update copy operation is completed. If you
request the release pair operation while the update copy process is still in
progress, it may take a long time to complete the operation. However, when
you urgently need to release a TCz Asynchronous pair, you can perform the
release pair operation from the RCU. In this case, you will find the suspended
status at the MCU after performing the release pair operation from the RCU.