HP XP7 Storage - Manual (Page 124)

Using CGROUP
The following figure shows a simple example of the CGROUP FREEZE/RUN command implemented
in a GDPS environment.
Figure key:
1.
Read/write I/Os are issued from the host.
2. A failure occurs on an P-VOL, and the MCU splits the pair.
3. Split and extended long busy state are reported to the host.
4. The 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. Host operations are switched to remote site.
Command sequence example
You can issue CGROUP FREEZE/RUN commands manually or through automation (such as with
GDPS). The following is an example sequence of actions you may implement.
1.
Suspend host updates to all P-VOLs on the specified MCU.
2. Block the specified MCU-RCU path to stop update copy operations to S-VOLs.
If the specified MCU does not have any P-VOLs, the FREEZE command is run without performing
any operations (paths are not blocked, SCP is not indicated).
3. Change all P-VOLs to Split status.
4. Resume host updates to split P-VOLs.
5. Run the add RCU operation to reestablish the blocked remote paths. After paths are established,
make sure to specify the desired SCP time for the MCU using the Remote Web Console Edit
SCP Time window. The range for SCP time is 0 to 518,400 seconds (144 hours); the default
is 120 seconds.
NOTE: If your specified SCP time is 601 seconds or longer, the microcode version cannot
be downgraded to 70-03-xx-xx/xx or earlier. In this case, lower the SCP time setting to 600
seconds or less, downgrade, then reset to the desired time.
6. After the path is reestablished, run the resynchronize pair operation.
Other TSO commands used with CGROUP
You can use the following TSO commands in your CGROUP FREEZE/RUN workflow:
•
Use CESTPATH to recover a blocked MCU-RCU path. Make sure to use the same parameters
as when the path was established.
•
After reestablishing the MCU-RCU path that was blocked, use CESTPAIR/RESYNC to
resynchronize the Cnt Ac-S Z pairs split by CGROUP/FREEZE.
124 Pair operations using PPRC