HP StorageWorks XP Disk Array Mainframe Host Attachment and Operations Guide (A5951-96154, September 2010)

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 XP 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
zVM (VM/ESA) Cache operations
When the storage system is managed under VM/ESA, the following SET CACHE commands are
effective across multiple SSIDs:
• SET CACHE SUBSYSTEM ON|OFF
• SET NVS SUBSYSTEM ON|OFF
• SET CACHEFW SUBSYSTEM ON|OFF
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