Virtual Storage Preservation VMSA VE Option During CP system generation, the installation can specify an option called the "Small CP Option". The Small CP option removes some of the normally resident CP nucleus functions that support remote CPo This effectively reduces the size of
the resident CP nucleus, making more storage available for the area where virtual
machine pages reside.
The Small CP option improves performance in environments where the real
processor storage size is 512K bytes or less.
Virtual storage preservation support is designed to preserve the contents of a virtu­
al machine if the system operator forces the machine off the system, if VM/SP abnormally terminates it, or if VM/SP itself abnormally terminates.
The user can specify at VM/SP system generation time which virtual machines are
to be saved. The contents of these virtual machines are saved in DASD space that
the VM/SP system programmer must previously allocate via the NAMESYS macro. The user can force a priority for the order in which multiple virtual
machines are saved; he does this through the SA VESEQ operand of the NAMESYS macro. The saved virtual machine is restored to the user via the IPL command. Normal recovery procedures or problem analysis for the saved virtual
machine may then be initiated by the user. To preserve its privacy and security, the
automatically saved virtual machine is made available only to previously specified
users. This saved virtual machine can be loaded into either a V =R or a normal
non- V =R machine. Subject to certain restraints, the user can dynamically control the option to save or
not to save the contents of the virtual machine (VMSAVE), and in which DASD area to save them (if there is more than one DASD area). If the user has a single DASD area defined, VMSA VE can be enabled either by the VMSA VE directory
option or by the SET VMSA VE ON command. A single VMSA VE area can be
designated for use by multiple virtual machines. However, the area is allocated to
only one user at a time; the user who first enables VNISA VE has priority. Normal
logoff, or invoking the SET VMSA VE OFF command relinquishes this VMSA VE
area.
The user with multiple DASD areas allocated must issue the SET VMSA VE name
command to enable the VMSA VE option. The SET VMSA VE OFF command
disables the VMSA VE option. Also, to relinquish the VMSA VE area, the user
may issue the SET VMS AVE OFF command, or logoff, or issue the SET VMSA VE name command specifying another area. The DASD save area can only
be relinquished by the owner of the data of the save area if data is stored in it. If
there is a saved system in the DASD area, the way to relinquish the area is for the
owner of the saved area to logon and issue the SET VMSA VE name command for
that area, then issue SET VMSA VE OFF command or LOGOFF. The current status of the VMSAVE option (ON or OFF) can be obtained from the
QUERY SET command. The QUERY VMSA VE command displays the current
status of the VMSAVE option, the names of the areas allocated for the user, the
page frames of each area, and the date and time that their contents were saved.
VM/SP 7
Termination
IPL
Priority
VMSA VE Areas
Target Areas
8 VM/SP System Programmer's Guide
If the VMSA VE option is enabled when conditions of termination other than
normal LOGOFF occur (such as a VM/SP abend and restart), the pages of the vir­
tual machine specified are saved in the previously allocated DASD area in the order
specified at system generation time by NAMESYS macro values in DMKSNT. After a virtual machine termination or a VM/SP abend in which virtual machine
contents were saved by the VMSA VE option, the IPL command initiated for the
designated VMSA VEd system by a logged-on user brings a page image copy of a
saved virtual machine into an active virtual machine, but does not give the saved
virtual machine control. The copy can always be dumped; however, it mayor may
not be executable.
The V=R area (if active) of the real machine is preserved if the system is perform­
ing a warm start. The V =R area is cleared if the system terminates to a hard wait
state or if a different V =R user logs on.
The SA VESEQ operand of the NAMESYS macro allows the user to force a priori­
ty in the saving order of multiple virtual machines. (The NAMESYS macro is
described in detail in the VM/SP Planning Guide and Reference.) The priority is
determined by number. The lower the number, the higher the priority. If two vir­
tual machines have the same priority, and both have the VMSA VE option enabled,
they are saved in the order in which they enabled VMSA VE. A sequence of VMSA VE disable followed by a VMSA VE enable causes a virtual machine to be
the last one on the chain --that is, last among the other virtual machines that have
the same SA VESEQ priority value.
If a high priority of SA VESEQ is specified for the production virtual machine, and
lower or equal priorities are specified for other virtual machines, the production
machine is saved first; other virtual machines are saved in the order in which the
virtual machines logged onto the system.
If different values of SAVESEQ are specified for each user (the range is 0-255), the priority of saving order for each virtual machine is predictable, depending on
which users are logged on when an abend occurs.
The VM/SP FORMAT/ALLOCATE program must format DASD space used for VMSAVE areas before any user can store into the area. Detailed information on
using the FORMAT/ALLOCATE program is contained in the VM / SP Operator's
Guide.
You can specify multiple VMSA VB target areas for a single user; you do this by
including in the DMKSNT module more than one NAMESYS macro with the same
USERID=operand. Different target areas are required if a user wishes to IPL a VMSA VE system and have the VMSA VE option enabled at the same time. Once the VMSA VE is enabled, the area referred to cannot be referenced by the IPL command until a recovery operation has been effected. Similarly, if a VMSA VE
area currently contains a saved system, it can be released only by the user who /'
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