$$BOPNLB $$BCLOSE $$BDUMP $$BOPENR $$BOPNR3 $$BOPNR2 Function under $$BOPEN-checks for supported DTF types, and initializes DTFs
in accordance with the device type. In the case of disk
files and tape data files, default tLBLs with the NOCHANGE option are issued. (The CMS STATE command is issued to
verify the existence of the input files.) $$BOPEN is invoked to supply additional extent information
for multi-extent real DOS data sets. $$BOPEN is also called
to initialize DTFs with EXTENT information for private and
system DOS libraries. The OPEN transient is responsible for
providing the proper extent information as a result of POINTR/POINTS requests. If a VSIM file is being opened (Byte 20 = X'28
1 in the ACB), control is passed to the VSAM OPEN routine. When opening DTFSD files for output or DTFCP/DTFDI
disk files for output, if a file exists on a CMS disk with
the same filename, filetype, and filemode, the file is erased.
Fetched by COBOL Compiler Phase 00 to read the appropriate
system or private source statement library directory record
and to determine whether or not active members are present
for the library.
Fetched by DOS/VS CLOSE macro expansion to deactivate a
file.
Fetched when an abnormal termination condition is
encountered. Control is not passed to a STXlT routine= CMS/DOS performs a CP dump to a virtual printer. The routine
is canceled.
Fetched by a DOS/VS OPENR macro expansion. The function cf $$BOPENR is to relocate all DTF table address constants frcm
the assembled addresses to executable storage addresses. At
entry to $$BOPENR, register 0 points to an assembled address
constant followed by a list of DTF addresses tables that
require address modification.
Fetched by $$BOPENR to relocate all DTF table address
constants for unit record DTFs.
Fetched by $$BOPNR3 to relocate all DTF table address
constants for DTFDI or DTFCP. EXCP Support in CMS/DOS CMS/DOS simulates
extent necessary
preceding section CMS/DOS." the EXCP (execute channel program) routines to the
to support the LIOCS routines described in the "DOS/VS Supervisor and I/C Macros Supported by Because CMS/DOS uses the DOS/VS LIOCS routines unchanged, it must
simulate all I/O at the EXCP level. The EXCP simulation routines convert
all the I/O that is in the CCi format to eMS physical 1/0 requests.
That is, CMS macros (such as RDBUF/WRBUF. CARDRD/CARDFH, PRINTIO, and WAITRD/TYPLIN) replace the CCW strings. If CMS/DOS is reading from Des ctisks, _I/O requests are handled via the DIAGNOSE interface. Part 3. Conversational Monitor System (eMS) 305

When an I/O operation completes, CMS/DOS posts the CCB with the return code. Partial RPS (rotational position sensing) support is
available for I/O operations to CMS disks because CMS uses RPS in its
channel programs. However, RPS is not supported when real DOS disks are
read. DOS/VS Supervisor Control Blocks Simulated by CMS/DOS CMS/DOS supports DOS/VS program development and execution for a single
partition: the background partition. Because eMS/DOS does not support
the four foreground partitions, it also does not simulate the associated
control blocks and fields for foreground partitions. CMS/DOS does
simulate the following DOS/VS supervisor control blocks: • ABTAB--Abnormal Termination Option Table • BBOX--Boundary Box • BGCOM--Background Partition Communication Region • EXCPW--Work area for module DMSXCP • FICL--First in Class • LUB--Logical Unit Block • NICL--Next in Class • PCTAB--program Check Option Table • PIBTAB--Program Information Table
• PIB2TAB--Program Information Block Table Extension • PUB--Physical Unit Block • PUBOWNER--Physical Unit Block Ownership Table
• SYSCOM--System Communication Region
For detailed descriptions of CMS/DOS control blocks, refer to the £2n!E21 §lg£! #QS!£. User Considerations and Responsibilities
A critical design assumption of CMS/DOS is that installations that use CMS/DOS will also use and have available a DOS/VS system. Therefore, if
you want to use CMS/DOS you must first order and install a DOS/'S system, Release 31, 32, or 33. Also, if you want to use the DOS/iS COBOL and DOS PL/I Optimizing compilers under CMS/DOS, you must order them and install them on your DOS/iS system.
There are several other facts you should consider if you plan CMS/DOS. The following sections describe some of the
considerations and responsibilities. DOS/VS System Generation and Updating
Considerations
to use
user
The CMS/DOS support in
provides the necessary
and system routines
Optimizing compilers image libraries. CMS may use a real DOS/VS system pack. CMS/DCS path and then fetches DOS/VS logical transients
directly from the DOS/VS COBOL and DOS PL/I directly from the DOS/VS system or private core
It is your responsibility to order a Release 31, 32, or 33 DOS/VS system and then generate it. Also, if you plan to use DOS compilers,
you must order the current level of the DOS/VS COBOL compiler and DCS PL/I Optimizing compiler and install them on the same DOS/VS system. 306 IBM VM/370 System Programmer's Guide