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

Performing TrueCopy for z/OS Pair Operations 6-11
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Pair Options
When you add new TrueCopy for z/OS pairs, you select the pair options on the
Add Pair dialog box. You can change the fence level, CFW data, and error level
pair options after a pair has been added. You cannot change the difference
management, DFW to R-VOL, or CT group of an existing pair. You need to
release and then restart the pair to change any of these options.
M-VOL Fence Level (TCz Synchronous only). Specifies the conditions under
which the MCU will reject write operations to the M-VOL, which is known as
“fencing.” This option is very important for disaster recovery planning. TCzA
M-VOLs are never fenced.
• Data: the M-VOL will be fenced when the MCU cannot successfully execute
an update copy operation for any reason. This setting is functionally
equivalent to the CRIT(YES-ALL) parameter for the CESTPAIR command.
• Status: the M-VOL will be fenced only if the MCU is not able to change the
R-VOL pair status to suspended when an update copy operation fails. If the
MCU changes the R-VOL pair status to suspended, subsequent write
operations to the M-VOL will be permitted, and the MCU will keep track of all
updates to the M-VOL while the pair is suspended. This setting is functionally
equivalent to the CRIT(YES-PATHS) parameter for the CESTPAIR command.
• Never: the M-VOL will never be fenced. If the TCz pair is suspended, write
operations to the M-VOL will be accepted. This setting is functionally
equivalent to the CRIT(NO) parameter for the CESTPAIR command.
Note: For further information on the CESTPAIR CRIT parameter and its two
modes of operation, CRIT(YES-PATHS) and CRIT(YES-ALL), please refer to the
IBM document Advanced Copy Services (SC35-0355) or DFSMS MVS V1
Remote Copy Guide and Reference (SC35-0169).
The CFW Data option specifies whether the CFW data will be copied to the R-
VOL:
• Copy to R-VOL: the MCU will copy the CFW data to the R-VOL.
Note: If a TrueCopy for z/OS pair is established using PPRC commands,
the CFW data option is set to the Copy to R-VOL setting.
Note: By using Remote Copy Function Switch, you can set the following
option with CESTPAIR: CFW data = only M-VOL. If you want to use this
function, please contact your Hitachi account team.
• Only M-VOL: the MCU will not copy the CFW data to the R-VOL. This setting
is recommended for two reasons: (1) copying the CFW data impacts storage
system performance, (2) CFW data is typically used for temporary files (e.g.,
sort work datasets) which are not usually required for disaster recovery.