HP XP P9500 Operation Manual page 31

LISTDATA COUNTS
LISTDATA COUNTS
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Subsystem counter reports. The cache statistics reflect the logical caching status of the volumes.
For the storage system, HP recommends that you set the nonvolatile storage (NVS) ON and
the DASD fast write (DFW) ON for all logical volumes. This will not affect the way the storage
system caches data for the logical volumes.
The default caching status for the storage system is:
CACHE ON for the storage system
◦
CACHE ON for all logical volumes
◦
◦ CACHE FAST WRITE ON for the storage system
◦ NVS OFF for the storage system (Change NVS to ON for the P9000 disk array.)
◦ DFW OFF for all volumes (Change DFW to ON for the P9000 disk array.)
NOTE: In normal cache replacement, bypass cache, or inhibit cache loading mode, the storage
system performs a special function to determine whether the data access pattern from the host is
sequential. If the access pattern is sequential, the storage system transfers contiguous tracks from
the disks to cache ahead of time to improve cache hit rate. Due to this advanced track transfer,
the storage system shows the number of tracks transferred from the disks to the cache slot at
DASD/CACHE of the SEQUENTIAL in TRANSFER OPERATIONS field in the storage system counters
report, even though the access mode is not sequential.
IDCAMS LISTDATA STATUS. The LISTDATA STATUS command generates status information for a
specific device within the storage system. The P9000 disk array reports two storage sizes:
Subsystem storage. This field shows capacity in bytes of cache. For a storage system with
more than one SSID, the cache is shared among the SSIDs instead of being logically divided.
This strategy ensures backup battery power for all cache in the storage system. For the storage
system, this field shows three-fourths (75%) of the total cache size.
Nonvolatile storage. This field shows capacity in bytes of random access cache with a backup
battery power source. For the storage system, this field shows one-fourth (25%) of the total
cache size.
IDCAMS SETCACHE. The storage system supports the IDCAMS SETCACHE commands, which manage
caching for subsystem storage through the use of one command (except for REINITIALIZE). The
following SETCACHE commands work for the subsystem storage across multiple SSIDs:
SETCACHE SUBSYSTEM ON|OFF
SETCACHE CACHEFASTWRITE ON|OFF
SETCACHE NVS ON|OFF
SETCACHE DESTAGE
NOTE: The SETCACHE REINITIALIZE command reinitializes only the logical storage system specified
by the SSID. You must issue the REINITIALIZE command once for each defined SSID.
DEVSERV PATHS. The DEVSERV PATHS command is defined as the number of LVIs that can be
specified by an operator (from 1 through 99). To display an entire storage system, enter the
DEVSERV command for several LVIs, as follows:
DEVSERV PATHS,100,64
DEVSERV PATHS,140,64
DEVSERV PATHS,180,64
DEVSERV PATHS,1C0,64
VOLUME(VOL128) UNIT(3390)
VOLUME(VOL192) UNIT(3390)
SUBSYSTEM
SUBSYSTEM
Mainframe operations 31