EXIT-SVC 3: This SiC is for CMS internal use only. It is used by the CMS--routIne DMSSLN to acquire an SVC SAVEAREA on return fron an
executing program that had been given control by LINK (SVC 6), XTCL (SVC 7) or ATTACH (SiC 42). Control is passed to the GETMAIN entry point in the storage resident routine. The mode is determined: VU, VC, EC. A call is made to GETBLK to obtain the block of storage. Control blocks
of two fullwcrds precede each section of available storage: (1) the
address of the next block, (2) the size of this block. The head of the
pointer string is located at the words MAINSTRt.- initial free block,
and MAINLIST - address of first link in chain cf free block pointers.
All options of GETMAIN are supported. Releases a block of free storage. If the block is part
of segmented storage, a control bl?ck of two full words is placed at the
beginning of the released area. Adjustment is made to include this
block in the chain of available areas. All options of FREE MAIN are
supported. Program transfer is controlled by the nucleus routine, DMSSLN. The LINK macro causes program contrel to be passed to a
designated phase. If the COMPSWT bit within the byte OSSFLAGS is on,
loading is done by calling LOADMOD to bring a CMS MODULE file into storagee If this flag is off, dynamic loading is initiated by calling LOAD. A GETMAIN is issued to obtain enough storage so that the loader (DMSLDR) may relocate the phase. in storage. A chain of link request
blocks is built to record the old SiC PSi, and the location and size of
the phase storage area. If the routine is already in storage,
determined by scanning the load request chain, no LOAD or LOADMOD is
done. Control is passed directly to the routine. CMS ignores the DCB and HIARCHY options; all other options of LINK are supported. XCTL first deletes the current phase from storage.
Processing then continues as for LINK-SVC 6, as previously described. CMS ignores The DCB and HIARCHY options; all other options of XCTL are
supported. LOAD-SVC 8: Control is passed to DMSSLN8 located in DMSSLN when a LOAD macro-is-issued. If the requested phase is not in storage, a LOAD or LOADMOD is issued to brLng it in. Control is then returned to the
caller. eMS the DCB and HIARCHY options; all other options of LOAD are supported. Control is passed to located in DMSSLN when a
DELETE macro is issued. Upon entry, DELETE checks to see whether the
.odule specified was loaded using LOADMOD or dynamically loaded by LOAD or INCLUDE. If it was loaded by LOADMOD control is returned to the
user. If it was dynamically loaded, the responsibility count is
decremented by one and if it reaches zero, the storage is released using PREEMAIN, and centrol is returned to the All options of DELETE
are supported. Code 4 is returned in register 15 if the phase is not
found. Control is passed to the SVC 10 entry point in DMSSMN. Storage management is analogous to SVC 4 and 5, respectively.
All options of GETMAIN and FREEMAIN are supported. Subpool specifications are ignored. CMS Method of Operation and program Organization 2-125

GETPOOL: Gets control via an OS LINK macro to IECQBFGI. IECQBPGI allocates an area of free storage using sets up a buffer
control block in the free storage, stores the address of the buffer
control block in the DCB, and then returns control to the caller. This routine (TIME) located in DHSSVT receives control
when a TIME macro instruction is issued. A call is made (by SIO or DIAGNOSE) to the RPQ software chronological timer device, X'OFP'. The
real time of day and date are returned to the calling program in a
specified form: decimal (DEC) binary (BIN), or timer units (TU). All
options of TIME except hundredths of a second HIe are supported. This routine (DMSSAB) receives control when either an
ABEND macro or an unsupported OS/360 SVC is issued. If an SVC 13 was
issued with the DUMP option and either a SYSUDUMP or SYSABEND ddname had
been defined via a call to DMSPLD (FILEDEP), a SNAP (SVC 51) specifying
PDATA=ALL is issued to dump user storage to the defined file. A check
is made to see if there are any outstanding STAE requests. If not, or
if an unsupported SVC was issued, DMSCWR is called to type a descriptive
error message at the terminal. Next, DMSCWT is called to wait until all
terminal activity has ceased, and then, control is passed to the ABEND
recovery routine. If a STAE macro was issued, a STAE work area is built
and control is passed to the STAE exit After the exit routine
is complete, a test is made to see if a retry routine was specified. If
so, control is passed to the retry routine. Otherwise, control passes
to DMSABN unless the task that had the ABEND was a subtask. In that
case, the resume PSW in the link block for the subtask is adjusted to
point to an EXIT instruction (SVC 3). The EXIT frees the subtask, and
the attaching task is redispatched. This routine (SPIE) receives centrol when a SPIE macro
instruction is issued. When it gets control, SPIE inserts the new program interruption control area (PICA) address into the program
interruption element (PIE). The program interruption element resides in
the program interruption handler (DMSITP). It then returns the address
of the old PICA to the calling program, sets the progra. .ask in the
calling program's PSW, and returns to the calling program. All options
of SPIE are supported. RESTORE is a NOP located in DHSSVT. svc to entry points in DMSSOP. If an OS disk
is specified, DMSSVT branches and links to DHSROS. See BLDL and PIND under description of BPAM routines in DMSSVT. See STOW under description of BPAe routines in DMSSVT. OPEN simulates the data management function of
opening one or more files. It is a nucleus routine and receives control from DMSITS when an executing program issues an OPEN macro instruction.
The OPEN macro causes an SVC to DMSSOP. DMSSOP simulates the OPEN macro. The DISP and RDBACK options are ignored by CMS; all other
options of OPEN and OPENJ are supported. CLOSE and TCLOSE are simulated in the nucleus
routine It receives control whenever a CLOSE or TCLOSE macro instruction is issued. The CLOSE macro causes an SVC to DMSSOP. DHSSCP simulates the CLOSE macro. eMS ignores the DISP option; all other
options of CLOSE and TeLOS! ara supported. This routine (DEVTYPE), located in DMSSVT, receives
control when a DEVTYPE macro is issued. Upon entry, DEVTYPE moves Device Characteristic Information for the requested data set into a user
specified area, and then returns control te the user. All options of DEVTYPE are sUFPorted, except RPS, which is ignored.
2-126 IBM VM/370 System Logic and Program Determination--Volume 2