DMSITS ---Passes the command line to DMSITS via an SVC 202. SVC handler. For a detailed description of the "Method of Operation for DMSITS." DMSCPF ---r1-the command could not be executed by the SVC command to CP to see if CP can execute it. DMSITS is the SVC handler, see
handler, passes the On return from processing the command line (label UPDAT), closes any
files that may have been opened during processing= Resets any flags or fields that may have been set during OS processing. DMSVSR that any fields set for VSAM processing are reset for CMS. Also ensures that the VSAM discontiguous shared segment is purqed@ DMSINT ---When the command line has been successfully executed, builds a CMS ready message for the user (label PRNREADY). DMSCWR ---Writes the ready message to the console. Returns control to DMSINT at label INLOOP2 to continue monitoring the CMS terminal session.
Method of Operation for DMSINT DMSINT, the console manager, maintains the continuity of operation of
the CMS command environment. The main control loop of DMSINT is
initiated by a call to DMSCRD to get the next command. When the command
is entered, DMSINT calls DMSINM to initialize the CPU time for the new
command and then puts it in standard parameter list form by calling the
scan function program DMSSCN. After calling DMSSCN, DMSINT checks to
see if an EXEC filetype exists with a filename of the typed-in command.
(For example, if ABC was typed in, it checks to see if ABC FXEC exists.)
If the EXEC file does exist, DMSINT adjusts register 1 to point to the
saae command as set up by DMSSCN, but preceded by CLa'EXEC', and then
issues an SVC 202 to call the corresponding EXEC procedure ('ABC EXEC' in the example).
If no such EXEC file exists for the first word typed in, DMSINT makes
a further check using the CMS abbreviation-check routine, DMSINA. If,
for example, the first word typed in had been 'E', DMSINT looks up 'E'
via the DMSINA routine. If an equivalent is found for 'E', DMSINT looks
for an EXEC file with the name of the equivalent word (for example, EDIT EXEC); if such a file is found, DMSINT adjusts register 1 as described
above to call EXEC and substitutes the equivalent word, EDIT, for the
first word typed in. Thus, if 'E' is a valid abbreviation for 'EDIT'
and the user has an EXEC file called EDIT EXEC, he invokes this when he merely types in 'E' from the terminal.
If no EXEC file is found either for the entered command name or for any equivalent found by DMSINA, DMSINT leaves the terminal command as
processed by DMSSCN and then issues an SVC 202 to pass control to DMSIIS which, in turn, passes control to the appropriate command program.
2-64 IBM VM/310 System Logic and Program Determination--Volume 2
When the command terminates execution, or if DMSITS cannot execute it,
the return code is passed in register 15.
A zero return code indicates successful completion of the command. A positive return code indicates that the command was completed, but
with an- apparent error; and a negative code returned by DMSITS indicates
that the typed in com.and could not be found or executed at all.
In the last case, DMSINT assumes that the coamand is a CP command and
issues a DIAGNOSE instruction to pass the command line to the CP environment. If the co.mand is not a CP command, DMSINT calls DMSCiR to
type a message indicating that the command is unknown and the main control loop of DMSINT is entered at the beginning.
If the return code from DMSITS is positive or zero, DMSINT saves the
return code hriefly and calls module DMSAUD to update the Master Pile Directory (MFD) on the user's appropriate user's disk. DMSINT also
frees the TXTLIB chain and releases pages of storage if required.
After updating the master file directory, DMSINT Checks the return
code that was passed back. If the code is zero, DMSINT types a ready
message and the processor time used by the given command. Control is
passed to the beginning of the main control leop of DMSINT. If the
return code is positive, an error message is typed, along with the
Frocessor time used. The command caused the typing of an error aessage of the format: DMSxxxnnnt 'text' where DMSxxx is the module name, nnn
is the message identification number, t is the message type, and 'text'
is the message explaining the error. Control is then passed to the
beginning of the main control loop.
Method of Operation for DMSITS DMSITS (INTSVC) is the CMS system SVC handling routine. Since CMS is SVC driven, the SVC interruption processor is more complex than the
other interruption processors.
The general operation of DMSITS is as follows:
1. The SVC new PSi (low-storage location X'60') contains, in the
address field, the address of DMSITS1. Thus, the DMSITS routine is
entered whenever a supervisor call is executed.
2. DMSITS allocates a system and user save area, as described belove The user save area is a register save area used by the routine,
which is invoked later as a result of the SVC call.
3. The called routine is invoked.
4. Upon return
deallocated. from the called routine, the save areas are
5. Control is returned to the caller (the routine which originally
made the SVC call).
The following expands upon various features of the general operation
that has just been described. CMS Method of Operation and Program organization 2-65
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