TRKBAL is a NOP located in DMSSVT. Returns control to CMS with an error code of 4 in register
15. This routine (iTO), located in D8SSVT, receives
control when either a iTO or a iTOR macro instruction is issued. For a iTO, it constructs a calling sequence to the DMSCiR function progra. to type the message at the terminal. (The address of the message and its
length are provided in the parameter list that results from the
expansion of the iTO macro instruction.) It then calls the DHSCiT function program to wait until all terminal I/O activity has ceased.
Next, it calls the DMSCiR function program to type the message at the
terminal and returns to the calling program. All options of iTO and iTOR are supported except those concerned with multiple console support.
For a iTOR macro instruction, this routine proceeds as described for iTO. However, after it has typed the message at the terminal it calls
the DMSCRD function program to read the user's reply from the terminal. When the user replies with a message, it moves the message to the buffer
specified in the iTOR parameter list, sets the completion bit in the BeB, and returns to the calling program. This routine (EXTRACT), located in D8SSVT receives
control when an EXTRACT macro is issued. Upon entry, EXTRACT clears tbe
user provided answer area and returns control to the user with a return
code of 4 in register 15. IDENTIFY-SVC 41: Located in DMSSVT, this routine creates a new load request-block-with the requested name and address if both are valid. The new entry is chained from the existing load request chain. The new name may be used in a LINK or ATTACH macro. Located in DMSSLN, ATTACH operates like a LINK (SVC 6),
with additional capabilities. The user is allowed to specify an exit
address to te taken upon return from the attached phase; also, an ECB is
posted when the attached phase has completed; and a STAI routine can be
specified in case the attached phase abends. The DCB, LPMOD, DP!OD, HIARCHY, GSPV, GSPL, SHSPV, SHSPL, SZERO, PURGE, ASYNCH, and TASKLIB
options are ignored; all other options of ATTACH are supported. Because CMS is not a multitasking operating system, a phase requested by tbe
ATTACH macro must return to CMS. CHAP is a NOP located in DMSSVT. TTIMER-SVC 46: Checks to ensure that the value in the timer (hex locaticn--SO) was set by an STIMER macro. If it <was, the value is
converted to an unsigned 32 bit binary number specifying 26 microsecond
units and is returned in register o. If the timer was not set by an STIMER macro a zero is returned in register 0, after setting register 0, the CANCEL oFt ion is checked. If it is not specified, control is
returned to the user. If it is specified, the timer value and exit
routine set by the STIMER macro are cancelled and control is returned to
the user. All oFtions of TTIMER are supported. STIMER-SVC 47: Checks to see if the WAIT option is specified. If so, control-is-returned to the user. If not, the specified timer interval
is converted to 13 microsecond units and stored in the timer (hex
location 50). If a timer completion exit routine is specified, it is
scheduled to be given control after completion of the specified time interval. If not, no indication of the completion of the tiae interval
is scheduled. After checking and handling any specified exit routine
address, control is returned to the user. All options of STIMER are
supported. The TASK option is treated as though the REAL option bad
been specified. CMS Method of operation and Program Organization 2-127

DEQ is a Nap located in DMSSVT. Control is passed to SNAP in DMSSVT when a SNAP macro is
issued. SNAP fills in a PLIST with a beginning and ending address and
calls DMPEXEC. DMPEXEC dumps the specified storage along with the
registers and low storage to the printer. Control is then returned to SNAP and SNAP checks to see if any more addresses are specified. It
continues calling DMPEXEC until all the specified addresses havg been dumped to the printer. Control is then returned to the user. Except
for SDATA, PDATA, and DCB, all options of the SNAP macro are processed
normally. SDATA and PDATA are ignored. processing for the DCB option
is as follows: The DCB address specified with SNAP is used to verify
that the file associated with the DCB is open. If it is not open,
control returns to the caller with a return code of 4. If the file is
open, the FCB associated with the file is checked for a device type of DUMMY. If the device type is DUMMY, control returns to the caller with
a return code of 0 and storage is not dumped. ENQ is a Nap located in DMSSVT. FREEDBUF-SVC 57: This routine (FREEDBUF) located in DMSSVT receives controI-when-a:- l"REEDBUF macro is issued. Upon ent:ry, E'REr!DBUF sets up
the correct DSECT registers and calls the FREEtBUF routine in DMSSBD. This routine returns the dynamically obtained buffer (BDAM) specified in
the to the DCB buffer control block chain. Control is then
returned to the DHSSYT routine which returns control to the user. All
the options of FREEDBUF are supported. STAB-SVC 60: This routine (STAB) located in DMSSVT receives control when-i--STAE macro is issued. Upon entry, STAE creates, overlays or
cancels a STAE control block (SCB) as requested. Control is then
returned to the user with one of the following return codes in register
15: An SCB is successfully created, overlaid or cancelled.
The user is attempting to cancel or overlay a nonexistent SCB. 0(0) , 1 10 or pointer to next SCBI 4 (4) lexit address
8 (8) I parameter list address
12 (C) I DETACH is a Nap located in D8SSVT. CBKPT is a Nap located in DMSSVT. .. I , I -J RDJFCB-SVC 64: This routine (RDJFCB) receives control when a RDJFCB .aero-Instruction is issued. When it gets control, RDJFCB obtains the
address of the JFCB fro. the DCBEXLST field in the DCB and sets the JFCB to zero. It then reads the simulated JFCB located in C8SCB that was
produced by issuing a FILEDEF into the closed area. RDJFCB calls the STATE function program to determine if the associated file exists. If
it does, RDJFCB returns to the calling program. If the file does not eXist, RDJFCB sets a switch in the DCB to indicate this and then returns
to the calling program. RDJFCB is located in DMSSVT. All the options
of RDJFCB are supported.
2-128 IBM VM/370 System Logic and Program Determination--Volume 2