Hitachi ShadowImage for z/OS user guide (HIT9503-96009, January 2008)

When the steady split operation starts, the pair status changes to SP-pending.ThewholeS-VOL
dataordifferentialdataatthattimeiscopiedandtheXP12000storagesystemperformsall
pending update copy operations to the T-VOL. When the steady split operation is complete, the
pair status changes to split, and you have full read/write access to the split T-VOL (even though it
is still reserved).The S-VOL also remains fully accessible. If you want to quickly finish the copy
operation to access the T-VOL, make the S-VOL offlinebeforetheoperation.
For information about Read/Write operations from host servers to S-VOLs and T-VOLs of Siz pairs
during steady split operation, see Table 4 on page 29.
Split operations cannot be performed on suspended pairs.
The following table shows read/write operations from the host servers to the volumes during the split
pair operation.
Table 4 Operations from Host Servers during Split Pair Operation
Operations
Volumes Quick Split Steady Split
S-VOL
Both areas which are not copied and areas which are
already copied can be read as usual.
Read
T-VOL
The areas which are
already copied can be
read as usual.
If the host server tries
to read the area which
is not copied yet, Siz
copies that area from the
S-VOL, and then the host
server reads the area
after the copy operation
completes. The result is
thesameaswhenthe
host server reads the area
which is already copied.
Cannot be read. Read
processing finishes
abnormally.
S-VOL
Write operation for the area which is already copied
to the T-VOL is performed normally.
If the host server tries to write data to the area which
is not copied yet, new data is written after the old
data is copied to the T-VOL. S-VOL data during the
split operation is copied to the T-VOL.
Write
T-VOL
The areas which are
already copied can be
written as usual.
If the host server tries to
write data to the area
which is not copied yet,
Siz copies that area from
the S-VOL, and then the
host server writes data to
the area after the copy
operation completes.
The result is the same
as when the host server
writes data to the area
which is already copied.
Cannot be written.
Write processing finishes
abnormally.
NOTE:
The CSUSPEND and PPRCOPY SUSPEND commands allow you to split Siz volume pairs. See
Chapter 5 on page 99 for more information on using PPRC commands to perform Siz operations
on the storage system.
Hitachi ShadowImage for z/OS user guide
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