If not found, the co.mand naae is considered to be an abbreviation
and the appropriate tables are examined. If found, the abbreviation
is replaced by its full equivalent and the search for an EXEC file
is repeated.
2. If there is no EXEC file, DMSINT executes SVC 202, passing the
scanned parameter list, with the cOmmand name in the first eight
bytes. DMSITS will perform the search described for SVC 202 in an
effort to execute the command.
3. If DMSITS returns to DMSINT with a return code of -3, indicating
that the search was unsuccessful, then DMSINT uses the CP DIAGNOSE facility to attempt to execute the command as a CP command.
4. If all of these searches fail, then DMSINT displays the error
message UNKNOWN CP/CMS COMMAND. See Figure 4 for a description of this search a command na:e. USER AND TRANSIENT PROGRAM AREAS Two areas can hold programs that are loaded from disk. These are called
the user program area and the transient program area. (See Figure 3 for
a description of CMS storage usage.) A summary of CP, CMS. IPCS, and RSCS modules and their attributes, including whether they reside in the
user program area or the transient area is contained in the 2 The user program area starts at location X'20000' and extends upward
to the loader tables. Generally, all user programs and certain system commands (such as EDIT, and COPYFILE) are executed in the user program
area. Since only one program cari 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 that is also intended to te executed in the user
program area.
The transient program area is tvo pages long, extending from location X'EOOO' to location X'PPPP'. It provides an area for system commands that 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 PSi system mask disabled for I/O 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 JS 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 OS 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 DMSSVT. For example, a program being executed in the transient program area may not
invoke the RENAME command. In addition, it may not invoke the OS 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. CMS Introduction 2-29

Figure 4. CMS Co •• and (and Request) Processing Notes
Pass contfol to the routine !In the nucleus. userarea'toe.ecute the command
1. If the terminal line was actually from an EXEC file, or if the
command SET IMPEX OFF has been executed, implied EXEC is not In effect.
2. A -3 return code md,cates SVC 202 processing did not find
the command.
3. If the terminal hne was actually from an EXEC file, or if the
command SET IMPEX OFF has been executed, implied CP 15 not In effect.
2-30 IBM VM/370 System Logic and Program Determination--Volume 2