z/VM: CP Commands and Utilities Reference - z/VM - IBM

SET NVS
SET NVS
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Set
NVS
Authorization
Purpose
Operands
Usage Notes
SUBSYStem
ON
OFF
Privilege Class: B
1304 z/VM: CP Commands and Utilities Reference
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rdev
rdev1-rdev2
Use SET NVS to make nonvolatile storage (NVS) available or unavailable within a
DASD subsystem. This command is valid for cache storage subsystems that
contain nonvolatile storage.
SUBSYStem
is an optional keyword that specifies that the entire storage subsystem is
affected by this command, regardless of which device within the subsystem
receives the order. This is the default (and only) value.
ON
indicates that the nonvolatile storage is to be made available to the subsystem.
OFF
indicates that the nonvolatile storage is to be made unavailable to the
subsystem.
rdev
rdev1-rdev2
is the real device number, a list of real device numbers, or a range of real
device numbers of devices in the subsystem.
1. SET NVS is valid only for cache storage subsystems that have nonvolatile
storage installed. An error message is generated for storage subsystems that do
not have nonvolatile storage installed.
2. The caching function is always enabled on RAID (Redundant Array of
Independent Disks) technology DASD such as the Enterprise Storage Server
(supported under VM in 3990 emulation mode). For these types of DASD, the
device accepts but ignores this command; the caching function cannot be
modified by the user. The caching function for these types will always appear as
ON in related query commands.
3. Certain error messages may result if the subsystem is not in the correct mode
to accept the SET NVS command. See error message HCP296E for more
information.
4. If DASD fastwrite has previously been activated for any device, the DASD
fastwrite function becomes operational when nonvolatile storage is made
available for subsystem use.
5. Making nonvolatile storage unavailable for subsystem use causes a destage of
all modified DASD fastwrite data in the subsystem.
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