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

Using PPRC Commands for TrueCopy for z/OS A-35
Hitachi Universal Storage Platform V TrueCopy for IBM z/OS User’s Guide
Using the CGROUP Command
Figure A.4 shows a simplified operational example of the CGROUP
(FREEZE/RUN) command implemented in a GDPS environment. The CGROUP
(FREEZE/RUN) TSO command can be issued by the user or through
automation (such as GDPS) to perform the following sequence of actions:
1. Suspend host updates to all TCz M-VOLs on the specified MCU.
2. Block the specified MCU-RCU path to stop update copy operations to the R-
VOLs.
3. Change all TCz M-VOLs on the specified MCU to suspended.
4. Resume host updates to the suspended M-VOLs.
5. The add RCU operation (CESTPATH) must be performed to re-establish the
blocked logical paths. After the MCU-RCU path is re-established, the
resynchronize pair operation (CESTPAIR/RESYNC) must be performed to
resynchronize the suspended pairs.
GDPS Host
Disk Subs
y
stem MCU #1
Failure
Disk Subs
y
stem MCU #2
(1)
(2)
(3)
(4)
(5)
(5)
(6)
(6)
(7) (8)
TCz M-VOL
(1) Read/write I/Os are issued from the host.
(2) A failure occurs on a TCz M-VOL, and the MCU suspends the pair.
(3) Suspend and extended long busy state are reported to the host.
(4) Host reports IEA494I with extended long busy state.
(5) CGROUP/FREEZE commands are issued to groups.
(6) SCP sense bytes are reported if an I/O is issued to a frozen volume.
(7) I/Os are queued at the host.
(8) Switch to remote (secondary) site.
Figure A- 3 Overview of GDPS Operations