e. For disk files (DTFxx), the LUB is verified to ensure that the
logical unit bas been assigned.1 check is made to ensure that
theDOSCB exists for the DTF filename. For disk output files,
the address of the appropriateIOAREl is placed in IOREG. For
disk input files, the existence of the file is verified via a
call toDKSSST. Also, EXTENT information is initialized and
theOPEl bit is posted.
f. DTFDT andDTFCP are separate DTF types that could describe any of the above devices.
4. After all files in the table have been opened,DKSBOP returns
control to the problemprogram via SVC 11.
5. If errors are encountered duringDMSBOP processing, an error
message is issued and returnis .ade via SVC 6.
TheCftS/DOS routine that processes CLOSE requests is DMSCLS, whose logiC
is analogous to that ofDKSBOP, the OPEN routine described above: when CLOSE expands, register 1 points to $BCLOSE and register 0 points to the
list of DTF/ACB addresses. The same table containing DTFs and lCBs used
to open files is also used to close those files. Eachentry in the
tableis processed as it occurs, with control passing to a VSAM CLOSE routine ($$BCVS1K) when an ICB is encountered. The OPEN bit is then
turned off.PROCESS CMS/DOS EXECUTION-RELATED CONTROL The CMS/DOS FETCH and DOSLKED com.ands simulate the operation of the DOS/VS fetch routines and the DOS/VS Linkage Editor. The three CMS .odules that perform this simulation are: • DKSFET--Prcvide an interface to interpret the DOS FETCH command line
and execute the phase, ifSTART is specified on the command line. • DftSFCH--Bring into storage a specified phase from a system or private
core-image library or from aCMS DOSLIB library. • DMSDLK--Link edit the relocatable output of the CMS/DOS language
translators to create executableprograms. The DOS/'S FETCH function is simulated by CMS .odules DMSFET and DMSFCH. The main control block used during a FETCH operation is FCHSECT, which
contains addressing information required for I/O operations.
The FETCH command line invokes module This module first
validates thecommand line and issues a FILEDEF for the DOSLIB file. It
then issues a FILEDEF for aDOSLIB file. DKSFE7 then issues a DOS SVC 4, which invokes the module DMSFCH to perform the actual FETCH
operation.
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logical unit bas been assigned.
the
the address of the appropriate
disk input files, the existence of the file is verified via a
call to
the
f. DTFDT and
4. After all files in the table have been opened,
control to the problem
5. If errors are encountered during
message is issued and return
The
is analogous to that of
list of DTF/ACB addresses. The same table containing DTFs and lCBs used
to open files is also used to close those files. Each
table
turned off.
and execute the phase, if
core-image library or from a
translators to create executable
contains addressing information required for I/O operations.
The FETCH command line invokes module
validates the
then issues a FILEDEF for a
operation.
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