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

SET DASDFW
SET DASDFW
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Set
Authorization
Purpose
DASDFW
Operands
Usage Notes
DEVICE
Privilege Class: B
Use SET DASDFW to activate or deactivate the DASD fast write function for
devices in a DASD subsystem. This command is valid for cache storage
subsystems that support the DASD fast write function.
Note: Although the SET DASDFW ON command activates the DASD fast write
function, it does not necessarily cause immediate DASD fast write operation.
For the DASD fast write function to operate, both the subsystem cache and
nonvolatile storage must be available and both caching and DASD fast write
must be activated for the device.
DEVICE
specifies that the DASD fast write function is to be activated or deactivated for
the specified devices. It is the default (and only) value.
ON
ON
OFF
FORCEOFF
1236 z/VM: CP Commands and Utilities Reference
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rdev
rdev1-rdev2
indicates that the DASD fast write function is to be activated for the specified
devices.
OFF
indicates that the DASD fast write function is to be deactivated for the specified
devices.
FORCEOFF
indicates that the DASD fast write function is to be unconditionally deactivated
for the specified device, regardless of any internal subsystem errors. This
operand should only be used when absolutely necessary, because there is a
possibility of loss of data.
rdev
rdev1-rdev2
is the real device number, a list of real device numbers, or a range of real
device numbers of devices for which the DASD fast write function is to be
activated or deactivated.
1. The SET DASDFW command is only valid for storage subsystems that contain
nonvolatile storage (NVS) and support the DASD fast write function. An error
message is generated if the subsystem containing a specified device does not
support this function.
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