1: !AI± -- Handled by DMSDOS ••• informs system programs to wait for a
system event to take place before processing can continue. WAIT is an
effective NOP for CMS/DOS. 8: Handled by DMSDOS ••• temporarily returns control to a problem program. The address of the problem to which control is being passed is
contained in register O. This address is stored in the SVC save area OLDPSW field and control is passed to the CMS SVC handler (DMSlTS). 2: Handled by DMSDOS ••• returns control to system program (i.e. a
user program has been given control, as in the case of SVC 8, and must
return control to the system routine, a $$$$B-Transient routine, that
called it). SVC 11: Handled by DMSDOS ••• returns control $$$$=B transient routine. Uses the SiC save
to the calling program.
to a problem program from a
area OLDPSW field to return ll: Handled by DMSDOS ••• resets flags in the linkage control byte of
the Partition Communication Region (BGCOM) to zero; also, provides the
user the capability to use a mask to set the value of this same byte.
In both cases, the SVC routine that handles the request performs an AND operation to accomplish the function. 1!: -- Handled by DMSDOS ••• normally terminates execution of a
problem program. Clears control blocks and resets control words. SiC 16: Handled by ••• establishes linkage with or terminates IInkage to a user's program check routine. Locates the appropriate PC option table entry. If contents of register 0 is zero, terminates
linkage: stores a zero into the routine address field of the PC option
table. If register 0 is non-zero, the address of the PC routine and the
save area address is passed to the STIlT macro. If a STXlT PC routine
is already active, the complement of the new routine address is placed
in the PC option table; if no STXIT PC routine is active, both the new
routine address and the save area address are Flaced in the PC option
table. 11: Handled by DMSDOS ••• provides supervisory support for the EXIT macro. Locates appropriate PC option table entry and restores user's
registers and PSi. Stores the address of the PC routine in the PC option table and returns to the next sequential address in the
interrupted program. l§: Handled by DMSDOS ••• validates address limits. Checks the limits
passed in registers 1 and 2 and either returns control to the caller or
writes an error message. JJ: Handled by DMSDOS ••• provides the address of the
partition communication region (BGCOM). Returns the address of BGCOM in
register 1. Handled by DMSDOS ••• supports the GETlME macro. Updates the date
field in the partition communications region Jl: Handled by DMSDOS ••• establishes linkage to or terminates linkage
from a user's abnormal termination routine. Locate the AB table entry_ If register 0 contains zeros, terminates linkage: if the AB routine is
active, stores zeros into the routine address field of the AB option
table. If the AB routine is net active, stores zeros into both the
routine address field and the save area field of the AB option table.
If register 0 is non-zero, establishes linkage: passes the address of
the AB routine and the save area address to the STXIT AB macro. If STXlT AB is active, the complement of the AB routine address is stored CMS Method of Operation and program Organization 2-145

in the AB option table. If STXIT AB is not active, both the address of
the new AB routine and the address of the save area are placed in the
option table. Handled by DMSDOS ••• signals the completion of a system event. SVC 50: Handled by DMSDOS ••• issues an error message and terminates the Issued by a LIOCS routine when that routine is requested to
perform a function it could not perform. tl: GETVIS -- Handled by DMSDOS ••• used by VSAM to scratch
storage; storage for a relocatable VSAM routine. Storage is obtained from the user. free storage area and the address of the
storage is returned in Register 1. §l: GETVIS. Handled by DMSDOS ••• returns storage obtained by a
Address of the area to be returned is pointed to by Register 1. nSR -- by DMSDOS ••. VSAM uses SVC 63 to that
system resources are updated serially, so that two or more attempts to modify the same data at the same time do not succeed. A table of
counters (RURTBL) is kept for system resources. These counters are
posted when a request is made for system resources. If a resource is
already in use, a return code of eight is placed in register O. If the
resource is available, a zero is returned in Register O. SVC 64: RELEASE -- Handled by DMSDOS ••• VSAM uses SVC 64 to release a system resource-obtained via USE SVC. The appropriate counter in RURTEL is decremented by one each ti.e a resource is SVC 65: CDLOAD -- Handled by DMSDOS •• a relocatable VSAM phase Into-storage-unless that phase has already been loaded.
If an anchor table is available, it is searched for the phase. If
the phase is found, its load pOint, entry point, and length are returned
in registers 0, 1, and 14, respectively, and register 15 contains zeros.
If the phase is not found in the anchor table, DHSFCH is called to
search for it. If the phase is found in the discontiguous shared
segment, return is made to the requestor as above.
If the phase was found, but not loaded, storage is obtained for it
via the GETVIS SVC. DMSFCH is called again to load the phase into the
storage just obtained. An anchor table is then built in the user area
(unless one already exists) and return to the caller is then made as
described above. §§: -- Handled by DMSDOS ••• determines whether the problem program is in real or virtual mode. Register 0 contains zero on
return if the program is running in virtual .ode. SVC 75: -- Handled by DMSDOS ••• used by VSAM I/O routines to attaIn a sector number for 3330 or 3340 devices. The appropriate sector
value is calculated from input supplied in registers 1 and O. The
sector number (from 0 to 127) is returned in register o. Certain DOS SVCs are treated as no-ops by CMSjDOS and other DOS/VS SVCs are Dot supported. These are listed below. 22: Handled by DMSDOS ••• provides supervisory support for the EXIT macro. The AB option of the EXIT macro provides an exit from the
abnormal task termination routine and continues the task.
2-146 IBM VM/370 System Logic and Program Determination--Volume 2