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

LOCK
Usage Notes
572 z/VM: CP Commands and Utilities Reference
Table 14. Page Number Derivation (continued)
2000-2FFF 2
.
1A000-1AFFF 1A
.
lastpage
is the hexadecimal number value of the last user, system, or address space
page to be brought into storage and locked. If only one page is to be brought
into storage, firstpage must be the same as lastpage.
SYMBOL symbol
has no effect and is retained only for compatibility with previous releases. All
symbols are considered resident, which means they cannot be locked or
unlocked. When used with the SYMBOL keyword, you can specify symbol as a
pattern by using asterisks (*) in place of one or more characters and percent
signs (%) in place of exactly one character.
symbol
has no effect and is retained only for compatibility with previous releases.
MAP
specifies whether a map of the storage pages locked should be displayed. MAP
is the default with symbol.
1. In the primary address space the first and last page numbers are treated as real
addresses. They are prefixed with the prefix register value of the base virtual
CPU of the target virtual machine.
In other address spaces, the first and last page numbers are treated as
absolute addresses. Prefixing is not applied to these addresses.
2. If the reserved page frames option is already in use by another virtual machine,
you can use the LOCK command to enhance the efficiency of a particular virtual
machine by keeping pages that are frequently referred to (such as page zero of
the virtual machine’s primary address space) in real storage. If the number of
page frames available for paging is limited, you should not enter the LOCK
command without the approval of your system programmer.
3. If too many pages of real storage are locked, the remaining virtual machines
may not have enough page frames available to operate efficiently. The
performance of all virtual machines may be severely degraded because of the
excessive contention for the available page frames.
4. Once a page of a virtual machine’s storage is locked, it remains locked until one
of these events occurs:
v The CP UNLOCK command is issued for the page.
v A SYSTEM CLEAR command is issued.
v The page is released by a DIAGNOSE X'10' instruction or a TEST BLOCK
instruction.
v A MAPMDISK DEFINE operation is issued for the page.
v A CP command causes an implicit system-reset-clear operation (for example,
DEFINE STORAGE, LOGOFF, and some forms of the IPL command).
.
.