Page of GC20-1806-9 As Updated April 1, 1981 by TNL GN25-0834 LOCK Use the LOCK command to permanently lock in real storage selected pages
of the 'pageable CP nucleus or of a user's virtual storage, thus
excluding them from future paging activity.
The LOCK command can enhance the efficiency OL a particular virtual machine by keeping high activity pages such as virtual page zero in real
storage if the reserved page frames option is already in use by some
other virtual machine. If the amount of page frames available for
paging is limited, the LOCK command should not be issued without the
approval of the systems programmer. Note: If too many pages of real storage are locked, the remaining
virtual machines may not have enough available page frames left to
operate Throughput may then be severely degraded in all
virtual machines because of excessive contention for the remaining
available page frames. Once a page is locked, it remains locked until either the user logs
off the system or you issue the UNLOCK command for that page. If a user
wi th the "locked pages" option in effect should re- IPL his system or
load another system, the locked pages are unlocked and available to the
system being loaded. Note that in the attached processor environment,
shared pages cannot be locked. Once the virtual=real area is unlocked,
a lock cannot be issued to run another V=R machine until VM/370 is
reloaded.
In uniprocessor mode you can lock a shared page but, if the shared
page becomes nonshared, the system unlocks it., In addition, if a
protected shared page locked and it is changed, the system unlocks
it.
The virtual pages locked in processor storage are blocks of 4K (4096) bytes. This block of storage need not represent all of the user's
virtual storage. The LOCK command may be issued as many times as
required for one virtual machine to lock noncontiguous pages of storage.
The remaining virtual machine storage blocks may remain pageable. The format o-f the LOCK colI-mand is; LOCK {
userid } firstpage lastpage [MAP] SYSTEM L---- ______________________________________________________________________ __ userid SYSTEM firstpage
is the user identification of a logged-on user.
locks one or more of the pageable CP pages6 The pageable
page(s) are locked until released by the UNLOCK command.
is the hexadecimal value of the first user page to ·be brought
into storage and locked.
lastpage is the hexadecimal value of the last user page to be brought
into storage and locked. If only one page 1S to be brought
into storage, lastpage must be the as firstpage. 90 VM/370 operator's Guide

MAP prints a map of the virtual storage pages locked and the real
page that is assigned for each page locked. The response to
the MAP operand is: VIRTPG virt-firstpage
virt-Iastpage REALPG real-firstpage
real-Iastpage !Qte: If you omit the MAP operand from a LOCK com.and and you later want to find the real page, reissue the LOCK command with the MAP operand. No intervening UNLOCK is required.
The SYSTEM and MAP operand are useful when you wish to examine (via DCP) or Bodify (via STCP) a page that is normally not resident (such as
console function routines). The KAP operand locates the real page for
display purposes. Page numbers are defined as follows:
Storage Locations
(in hexadeci.al) OOO-OFFF 1000-1FFF 2000-2FFF 12000-12FFF Page Number o
1
2
12
1. For firstpage and lastpage, only the page numbers are specified.
For example, to locK USERA's virtual storage locations X'12000' to X'2eooo' in real storage, the following command should be given: LOCK USERA 12 2C
To lock the first three pages of a USERA's storage, enter: LOCK USERA 0 2
2. To lock a CP page for display purposes, key in the following LOCK SYSTEM 2A 2A KAP VIRTPG REILPG} response to the MAP operand 021000 04FOOO DCP 4F038- 4F048 etc. UNLOCK SYSTEK 21 2A COMMAND COMPLETE Section 3. CP Commands 91