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

Performing TrueCopy for z/OS Pair Operations 6-5
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Note: If the time out error occurs during the Add Pair operation, the copy
operation may not be executed correctly in the order that you have set
with the Priority parameter. The time out error may be caused by the CU
configuration or a remote copy path error. Review the error, release the
pair with the error, and then retry the Add Pair operation.
• Difference Management: Select Auto, Cylinder or Track as the basis for
managing the differential data. The default is Auto. When you select Auto,
either Cylinder or Track is selected depending upon the basis size of the
logical volume image.
• CFW Data: 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.
– 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 subsystem performance, (2) CFW data is typically used for
temporary files (e.g., sort work datasets) which are not usually required
for disaster recovery.
Note: When you create a TCz pair, and if you select only M-VOL for the
CFW data option, the data set which is updated by CFW in M-VOL cannot
be used in R-VOL. To use this data set in R-VOL, release a TCz pair, and
format the data set.
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.
• DFW to R-VOL (Synchronous only): Specifies whether the MCU will suspend
a TCz pair when the RCU cannot execute DFW to the R-VOL:
– DFW not required: the pair is not suspended when DFW to the R-VOL is
blocked.
– DFW required: the pair is suspended when DFW to the R-VOL is
blocked.
Caution: The interaction of the DFW required setting and the M-VOL
fence level setting can cause a host application to fail with a permanent I/O
error when attempting to update an M-VOL. Keep track of which pairs have
the DFW required setting, and make sure that DFW to the R-VOL is not
blocked.
Note: If a TrueCopy for z/OS pair is established using PPRC commands,
the DFW to R-VOL option is set to the DFW not required setting.
Asynchronous Parameters (Asynchronous only):
• CT Group: consistency group for the new pair(s). Consistency groups which
have already been added to the current MCU are displayed.
Note: This option cannot be changed after a pair has been added.