Hitachi ShadowImage for z/OS user guide (HIT9503-96004, June 2006)

26 ShadowImage for the XP1024/XP128/XP12000/XP10000
and quick restore cannot be performed on suspended pairs. While the resync operation for a split pair can
be very fast, the resync operation for a suspended pair will take as long as the initial copy operation.
The XP1024/XP128/XP12000/XP10000 will automatically suspend an SI390 pair when it cannot keep
the pair mirrored for any reason. When the XP1024/XP128/XP12000/XP10000 suspends a pair, sense
information is generated to notify the host. The XP1024/XP128/XP12000/XP10000 will automatically
suspend an SI390 pair under the following conditions:
• When the XP1024/XP128/XP12000/XP10000 detects an error condition related to an update copy
operation.
• When the S-VOL and/or T-VOL track map in shared memory is lost (for example, due to offline
microprogram exchange). This applies to SP-pend and V-split pairs only. For duplex, split, resync, or
resync-r pairs, the pair is not suspended but the entire S-VOL (T-VOL for reverse resync) is marked as
difference data.
Use the Suspend Volume Pair window (see ”Suspending ShadowImage Pairs” on page 60) to suspend
SI390 pairs. When a pair is suspended, the pair status changes to suspended. When the resync operation
starts, the pair status changes to resync. The S-VOL remains fully accessible while suspended and during
the resync operation. Use the Resynchronize Volume Pair window (see ”Resynchronizing ShadowImage
Pairs” on page 58) to resynchronize suspended SI390 pairs.
NOTE: The PPRC commands do not support the SI390 suspend operation. You must use the SI390 remote
console software to suspend SI390 pairs. The CSUSPEND and PPRCOPY SUSPEND commands execute an
SI390 split operation instead of a suspend operation. For more information on using PPRC commands to
perform SI390 operations on the XP1024/XP128/XP12000/XP10000, see ”Using PPRC Commands for
ShadowImage” on page 71.
Delete Pair Operation
The SI390 delete pair operation stops the SI390 update copy operations to the T-VOL of the pair and
changes the pair status of both volumes to simplex. An SI390 pair can be deleted by the user at any time
except during the quick split operation (that is, any status except simplex and V-split). After you delete an
SI390 pair, the T-VOL is still not available for write operations until the reserve attribute is reset.
Use the Delete Volume Pair window (see ”Deleting ShadowImage Pairs” on page 61) to delete SI390
pairs. When an SI390 pair is deleted, pending update copy operations for the pair are discarded, and
the status of the S-VOL and T-VOL is changed to simplex.
CAUTION: The T-VOL of a duplex pair may not be identical to its S-VOL, due to the asynchronous SI390
update copy operations. To synchronize the volumes before deleting the pair, you must split the pair first
(see ”Deleting ShadowImage Pairs” on page 61 for instructions).
ShadowImage Options
By using the SI390 options, you can extend the standard SI390 operations such as the add pair and
resync pair operations. The following table shows the options that are currently available.
Table 6 Types of ShadowImage options
Option Type Features Requirement
Swap&Freeze Swap&Freeze option suppresses the update
copy. For details, see ”Swap&Freeze Option”
on page 27.
You must change the subsystem setting to allow
the quick restore operation.
Host I/O
Performance
Host I/O Performance option suppresses the
copy operations by ShadowImage for z/OS.
For details, see ”Host I/O Performance Option”
on page 27.
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