Before mounting a DASD volume to reserve it for the system, operators
first must ensure that jobs requiring the volume are not selected
by an initiator. Operators can hold up job selection by one of the
following:
- Using the TYPRUN=HOLD parameter on the job statement.
- Using the appropriate subsystem command.
- Assigning the job to a job class and not activating that class
for subsystem scheduling.
To reserve the volume, the operator then must:
- Use the VARY command to put the device offline to
each sharing
system and wait
for the offline message in each system. The device does not go offline
until the message is issued.
- Use the MOUNT command to notify each sharing system of the unit
where the new volume is being
placed, and to put the volume in reserved status.
- Use the MOUNT command to mount the volume.
After the volume is mounted, operators can use a JES command or
activate the class for subsystem scheduling.
Note: - To stop I/O to a shared device or group of devices, operators
can use IOACTION QUIESCE. See z/OS MVS System Commands
for
syntax and examples.
- If there is a hardware failure on a device other than the system
residence device, the operators must vary the failing device offline
on all sharing systems. Operators can then mount the shared volume
on another shared device, if one is available, as long as parallel
mount procedures occur on all sharing systems.
- Operators can release a reserved device and remove a path to it
by issuing
CONFIG CHP,OFFLINE,FORCE. If operators
try to remove a path to a reserved device with any other CONFIG command
or with a VARY command, the system issues message IEE379I or IEE719I
and does not execute the
command.
- When you want a shared non-JES3 device to be allocated by only
one system, the operator of each system sharing the device should
use the VARY command to place the device offline on the sharing systems.