Generating Saved Systems By taking advantage of the SAVESYS command, system resources are not
committed to perform an IPL each time a system is loaded. Instead, the
saved system is located and page tables are initialized according to its
system name table entry. The saved system is not automatically loaded
at IPL time; however, its pages are brought into storage on demand as
the virtual machine operating system executes.
In addition to saving time by avoiding an IPL, a saved system can
share segments of reenterable code, thus making more efficient use of
real storage. This technique is especially valuable when using CMS. However, a shared segment cannot be initialized in the virtual = real
machine, via an IPL.
To generate a saved system: I • Assemble the NAMESYS macro instruction in module DMKSNT. I • Load a new control program nucleus. I • Load the system to be saved and then issue the SAVESYS command. When allocating DASD space for named systems, provide an extra page
for information purposes; do not overlay this area with subsequent named
systems.
The NAMESYS Macro for Saved Systems The NAMESYS macro is assembled by the installation system programmer and
is used to describe the location of the saved system. Shared segments
may be specified, but they must consist of reenterable code. When making additions, changes, or deletions to the system name table, the DMKSNT module must be reassembled. The GENERATE EXEC procedure has the facility to reassemble only the DMKSNT module. See the description of the GENERATE EXEC procedure in the Q.§1!.§gtig1! A DMKSNT ASSEMBLE module supplied with the system contains a dummy NAME TABLE. Either edit or update this module to include the NAMESYS macros describing your installation's named systems. Note that this
module may contain a PUNCH SPB card, which is used by the loader to
force this module to a 4K boundary when the CP system is built (a 12-2-9
multipunch must be specified in column 1 of an SPB). The format of the NAMESYS macro is:
r I label I I I I I I NAMESYS n'U ,I "')..,. 1'\ ,;..,1./ ...JII V SYSSIZE=nnnnnK,SYSNAME=name,VSYSRES=ccccCC, VSYSADR={cuu },SYSVOL=cccccc,SYSCYL=nnn, SYSSTRT=(cc,p) ,SYSPGCT=pppp, SYSPGNM=(nn,nn,nn-nn, ••• ) , SYSHRSG=(s,s, ••• ),
PROTECT = {QJ! } OFF -- -- ,...,. -......,. -- ..•. -, .. - J:,L V'j,;.r.:tii.I.,;.eJ.. .;:, -.. , I I I I I I I

April 1, 1981
label is any desired user label. SYSSIZE=nnnnnK is the amount of storage you must have available in
order to load the saved system. K must be specified. SYSNAME=name is the name (up to eight alphameric characters) given to the
system to be used for identification by the SAVESYS command.
The name selected must never be one that could be interpreted
as a hexadecimal device address (for "A" or "E"). VSYSRES=cccccc is the real volume serial number of the DASD volume containing
the virtual disk that is the system residence volume for the
system to be saved. VSYSADR=cuu is the virtual address of the virtual disk that is the system
residence volume for the system to be saved. SYSVOL=cccccc SYSCYL=nnn is the volume serial number (up to six alphameric characters)
of the DASD volume designated to receive the saved system.
This must be a CP-owned volume.
is the real starting cylinder of the virtual disk (specified
by VSYSRES and VSYSADR) that is the system residence volume
for the system to be saved. SYSSTRT= (cc ,p)
designates the starting cylinder (cc) and page address on SYSVOL. at which this named system is to be saved. During the SAVESYS and 1PL processing, this is used to generate the
"cylinder page and device" address for the DASD operations.
These numbers are specified in decimale
The number of pages written to this area is the total number
specified via the SYSPGNM operand, plus one information page. SYSPGCT=pppp is the total number of paqes
(that is, the total number SYSPGNM operand). This is
diqits.
(pppp) you specify to be saved
of pages you indicate via the
a decimal number, up to four
The STSPGCT operand is not required when assembling the NAMESYS macro VM/370 Release 3 MACLIBs. The macro
itself will calculate the number of pages to be saved. SYSPGNM=(nn,nn,nn-nn, ••• )
are the numbers of the pages to be saved. Pages may be
specified singly or in groups. For example: if pages 0, 4, and 10 throuqh 13 are to be saved, use the format: SYSPGNM=(0,4,10-13). Part 2. Control Program (CP) 133