Paqe of GC20-1807-7 As Updated April 1, 1981 by TNL GN25-0829
Name is now the
real name from the Synonym Table Yes SVC 202 name
Attempt to execute LOADMOD name
MODULE from disk Set RC =-3 Yes Yes Pass control to the
routine (in the nucleus, transient area, or user area) to
execute the
command
Upon completion, return to SVC routine I Figure 28. CMS Command (and Request) Processinq (Part 2 of 2)
262 IBM VM/370 System Programmer's Guide

USER AND TRANSIENT PROGRAM AREAS
Two areas bold programs that are loaded from disk. These areas are
called the user program area and the transient program area. (See Pigure 27 for a description of CMS storage usage.)
The user program area starts at location X'20000' and extends upward
to the loader tables. Generally, all user programs and certain syste. commands (sucb as EDIT, and COPYFILE) are executed in the user program
area. Since only one program can be executing in the user program area
at anyone time, it is impossible (without unpredictable results) for
one program being executed in the user program area to invoke, by means of SVC 202, a module tbat is also intended to be executed in the user
program area.
The transient program area is two pages long, extending from locaticn X'EOOO' to location X'FFFF'. It provides an area for system commands
tbat may also be invoked from the user program area by means of an SVC 202 call. When a transient module is called by an SVC, it is normally
executed with the PSW system mask disabled for IIO and external
interrupts.
The transient program area is also used to handle certain OS macro
simulation SVC calls. OS SVC calls are handled by the as simulation
routines located either in the CMSSEG discontiguous shared segment or in
the user program area, as close to the loader tables as possible. If
DMSITS cannot find the address of a supported as SVC handling routine.
then it loads the file DMSSVT MODULE into the transient area, and lets
that routine handle the SVC. A program being executed in the transient program area may not invoke
another program intended for execution in the transient program area.
including OS macro simulation SVC calls that are handled by For
example, a program being executed in the transient program area may not
invoke the RENAME command. In it may not invoke the as macro iTO, which generates an SVC 35, which is handled by DMSSVT. DMSITS starts the programs to be executed in the user program area
enabled for all interrupts but starts the programs to be executed in the
transient program area disabled for all interrupts. The individual
program may have to use the SSM (Set System Mask) instruction to change
the current status of its system mask. Part 3. Conversational Monitor System (CMS) 263