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

RETAIN XSTORAGE/XSTORE
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RETAIN
Authorization
Purpose
Operands
XSTorage
XSTore
Privilege Class: B
Use RETAIN XSTORAGE or RETAIN XSTORE to:
v Retain some or all Expanded Storage for the exclusive use of the control
program (CP). The size of Expanded Storage assigned to guest virtual machines
is the maximum size of Expanded Storage, less the amount of Expanded
Storage retained for control program use.
v Specify the maximum and minimum amounts of Expanded Storage that can be
used by the minidisk cache. The actual size of the XSTORE portion of the
minidisk cache varies and is determined dynamically by the activity of paging and
minidisk I/O. To change the size of the main storage portion of minidisk cache,
use the SET MDCACHE command.
ALL
specifies that all of Expanded Storage configured on the system is retained for
CP use.
NONE
specifies that none of the Expanded Storage configured on the system is
retained for CP use.
nnnnnnnnM
specifies the size expressed in megabytes of real Expanded Storage retained
for CP use.
MDCache
indicates that minidisk cache parameters are being changed.
ON
ALL
NONE
nnnnnnnnM
MDCache
ON
ALL
OFF
0M
minM
MAX
maxM
RETAIN XSTORAGE/XSTORE
indicates that CP uses the amount of XSTORE for minidisk cache that best
balances I/O and paging performance. This is the default. The amount of
XSTORE allotted to minidisk cache size can range from 0 MB to the size of the
CP partition. This is the default.
ALL
indicates that CP uses the CP partition of Expanded Storage exclusively for
minidisk cache. CP does no paging to Expanded Storage.
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Chapter 2. CP Commands 1173