HP StorageWorks XP Remote Web Console Software - Manual (Page 33)

When a TrueCopy for Mainframe Asynchronous pair is suspended, the C/T of the suspended
R-VOL is frozen. If the RCU can ensure the update sequence consistency between the suspended
R-VOL and the other R-VOLs in the consistency group, the R-VOL C/T is frozen at the latest
consistency time of the group. Otherwise, the R-VOL C/T is frozen at the time-stamp value of the
most recent update that was successfully copied to the R-VOL. The C/T of a suspended R-VOL may
be older than the C/T of other R-VOLs in the group, and if the entire group was not also suspended,
the consistency time of the group is still ticking. For suspended TrueCopy for Mainframe
Asynchronous R-VOLs, the TrueCopy for Mainframe Detailed Information dialog box displays
whether the C/T was frozen to the group or R-VOL time.
Once you have established TrueCopy for Mainframe Asynchronous operations, you should monitor
the consistency time of each group at the RCU(s). If the average delay is longer than your disaster
recovery design can accept, you should consider adding remote copy resources (for example,
paths, cache) and/or reducing the I/O workload to improve storage system performance. If the
delay between the M-VOL update and the corresponding R-VOL update reaches the time specified
by the Time Out [Copy Pending] group option, the MCU will suspend all affected pair(s) due to the
heavy I/O workload (at MCU or RCU). To prevent timeout errors, you can increase the Time Out
[Copy Pending] value, reduce I/O workload, and/or add remote copy resources.
This information is valid only when the timer type is System.
Group Operations
TrueCopy for Mainframe Async provides the following group-based operations to simplify and
expedite disaster/failure recovery procedures:
•
Group operations at the MCU:
Suspend all pairs in a consistency group (Group suspend option, supported by CSUSPEND
TSO command). ◦
◦ Resynchronize all suspended pairs in a consistency group (Group resynchronize option,
supported by the CESTPAIR TSO command with MODE=RESYNC).
◦ Release all pairs in a consistency group (Group release option, supported by CDELPAIR
TSO command).
•
Group operations at the RCU:
Suspend all pairs in a consistency group (Group suspend option, supported by CSUSPEND
TSO command). ◦
◦ Release all suspended pairs in a consistency group except for any inconsistent pairs (C/T
release option, not supported by CDELPAIR, CDELPAIR cannot be issued to the RCU).
◦ Release all pairs in a consistency group regardless of their consistency status (Group
release option, not supported by CDELPAIR, CDELPAIR cannot be issued to the RCU).
TrueCopy for Mainframe Asynchronous also provides the Error level pair option which is used to
trigger automatic suspension of an entire consistency group. When a TrueCopy for Mainframe
Asynchronous pair is suspended due to failure (not user-requested), this TrueCopy for Mainframe
Asynchronous pair option determines whether all pairs in the same consistency group will also be
suspended. If you select the Group error level for a TrueCopy for Mainframe Asynchronous pair,
all pairs in the same group will be suspended. If you select the Volume error level, only the affected
TrueCopy for Mainframe Asynchronous pair will be suspended.
The Error level pair option is very important for managing TrueCopy for Mainframe Asynchronous
groups and planning for disaster recovery. The Group error level should be selected for all TrueCopy
for Mainframe Asynchronous volumes which are essential to disaster recovery. Suspended TrueCopy
for Mainframe Asynchronous R-VOLs which have the Volume error level should not be used for
disaster recovery.
TrueCopy for Mainframe Async Consistency Group Operations 33