Hitachi ShadowImage for IBM z/OS User"s Guide (T5213-96002, June 2007)

About ShadowImage™ for IBM
®
z/OS
®
Operations 2-9
Hitachi ShadowImage™ for IBM
®
z/OS
®
User’s Guide
Legend
: At-Time Split function
S-VOL S-VOLS-VOL S-VOL
T-VOL T-VOLT-VOL T-VOL
I/O
Pairs in the same
consistency group
Host
Figure 2-5 Split pair operation by At Time Split (Specifying the Split
Time)
Suspend Pair Operation
The ShadowImage for z/OS suspend pair operation suspends the update copy
operations to the T-VOL of the pair. When an SIz pair is suspended, the USP V
storage system stops performing update copy operations to the T-VOL, and
the pair status changes to suspended. The storage system continues accepting
write I/O operations to the S-VOL, and marks the entire S-VOL track as
difference data. When a pairresync operation is performed on a suspended
pair, the pair status changes to resync and the entire S-VOL is copied to the
T-VOL. While the pairresync operation for a split pair can be very fast, the
pairresync operation for a suspended pair will take as long as the initial copy
operation.
The USP V storage system will automatically suspend an SIz pair when it
cannot keep the pair mirrored for any reason. When the storage system
suspends a pair, sense information is generated to notify the host. The storage
system will automatically suspend an SIz pair under the following conditions:
• When the storage system detects an error condition related to an update
copy operation, and
• When the differential bitmap in shared memory is lost (e.g., 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 copy) is marked as difference data.