communications are fully restored (all paths have normal status) before beginning I/O
operations to the M-VOL.
If the main system accepts an I/O for a M-VOL before this, all communications are restored,
the main system will suspend the pair and change M-VOL status to suspended-by RCU. The
main system cannot change the pair status of the R-VOL.
If power is removed from a remote system or from a data path component while Continuous
Access Synchronous Z operations are in progress, the main system detects the communication
failure, suspends all affected pairs, and generates SIMs reporting the failures. The main system
changes the M-VOL status to suspended-by RCU but cannot change the status of the R-VOLs.
If a main or remote system is powered off and the backup batteries are fully discharged while
Continuous Access Synchronous Z pairs are suspended, differential data is not be retained.
In this unlikely case, the system marks all tracks of all suspended Continuous Access
Synchronous Z M-VOL as modified so that the main system will perform the equivalent of an
entire initial copy operation when the pairs are resynchronized. R-VOL differential data is
used for the R-VOL write enable option.
Planned outage of the main disk array
A planned outage of the main system does not affect Continuous Access Synchronous Z.
Planned outage of the remote disk array or data path
You must split the Continuous Access Synchronous Z pairs in a remote system prior to a planned
outage of the system or to a data path component (for example, switch, channel extender).
Procedure 19 To perform a planned outage of a Continuous Access Synchronous Z remote system
or data path component
Identify the Continuous Access Synchronous Z M-VOLs that are paired with R-VOL in the remote
system that is to be powered off.
For data path outage, identify all M-VOLs in the main system that use the path or component
to be powered off.
You need to know the MCU, CU, and LDEV ID for each of the M-VOLs.
Connect to each main that contains affected M-VOLs, and split all affected Continuous Access
Synchronous Z pairs. Confirm the changed pair status.
Perform the planned outage of the remote system or data path.
When the remote system is fully powered on and ready, resynchronize the affected pairs at
each main. Confirm the pair status changes.
Planned outage of the main and remote systems
When you plan an outage of Continuous Access Synchronous Z main and remote systems at the
same time, the main system must be powered off first, and powered on last.
Procedure 20 To perform a planned outage of Continuous Access Synchronous Z main and remote
Perform the planned outage of the main system. Because a planned outage does not affect
synchronous pairs, nothing out of the ordinary must be done regarding the Continuous Access
Synchronous Z system or operations. Do not power-on the main system at this time.
If a remote system to be powered off is connected to a main system that is not powered off,
suspend the Continuous Access Synchronous Z pairs before powering off the remote system.
Perform the planned outage of the remote systems as described in previous section.
Power on the remote systems. Make sure that they are fully operational and ready to
resynchronize operations before powering on the main system.
Monitoring and maintenance