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

Responses
2. If the NVS or cache is not available when the SET DASDFW ON command is
issued, the DASD fast write function begins when these resources become
available. (For information on making these resources available to the
subsystem, see “SET CACHE” on page 1195 and “SET NVS” on page 1304.)
3. Attention: The FORCEOFF operand is intended only for recovery purposes
and can result in a loss of data. It should only be used after SET DASDFW OFF
has been issued to the device and the subsystem could not deactivate the
DASD fast write function because of internal errors.
4. SET DASDFW OFF may produce delayed responses. See “Delayed Responses
to CP Commands” on page 8 for more information.
5. This command may be issued to offline devices.
6. 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.
Response 1:
The following response is displayed when you enter SET DASDFW ON and is
repeated for each device specified on the command line.
rdev DASD fast write function has been activated.
If the originator of the command is not the system operator, the following response
is issued to the system operator and is also repeated for each device specified on
the command line.
rdev DASD fast write function was activated by userid.
rdev
is the real device number of a device for which the DASD fast write function
has been activated.
userid
is the ID of the user who issued the command.
Response 2:
Immediate Response: If you enter SET DASDFW FORCEOFF, or if the DASD fast
write function is deactivated immediately when you enter SET DASDFW OFF, the
following response is repeated for each device specified on the command line.
rdev DASD fast write function has been deactivated.
rdev
is the real device number of a device for which the DASD fast write function
has been deactivated.
Delayed Response: If you issued the SET DASDFW OFF command and the DASD
fast write function was not deactivated immediately, the following response is
displayed:
Command started: SET DASDFW OFF rdev.
When the DASD fast write function is deactivated, the following response is issued:
rdev DASD fast write function has been deactivated.
SET DASDFW
Chapter 2. CP Commands 1237