Command Operund Comments OPTION Executable only in the Cr'lS/DOS environment. Sets compilGr options for DOS/VS COBOL. PSERV Executable only in the Ci'1S/DOS environment. CopiGS and displays procedures in the VSE procedure libraries and/or spools the procedures to the CMS virtual printer und/ or punch.
QUERY UPSI Executable only in the environment. Displays current setting of Cr1S/DOS UPSI byte. OPTION Executable only in the Ct'lS/DOS environment. Displuys Cf1S/DOS compiler options. DOSLNCNT Displays the current number of SYSlST lines per page. DOS Displuys the current stutus (active or not uctive) of . DOSlIB Displays the names of ull CMS/DOS phase
libraries currently being searched for
executable phases.
LIBRARY Displays the names of all Ci1S·/DOS phase
libraries to be in addition to
the text and mucro libruries. RSERV Executable only in the CMS/DOS environment.
Copies and/or displays modul2s in a VSE relocatable library. Output can also be directed to the virtual printer or punch. SET DOS Makes the environment active or not
active. DOSLNCNT nn Specifies the number of SYSLST lines
per page. UPSI Executable only in the Ct'lS/DOS environment. Sets the Ct'lS/DOS UPS! byte. SSERV Executable only in the CNS/DOS environment.
Copies or displays books from the VSE source statement library. Output can also
be directed to the virtual printer or
punch.
Figure 43 (Part 2 of 2). Summary of Changes to Commands to Support Logical Unit Assignment
A logical unit is a symbolic name by which a program may refer to a real I/O
device without knowing the device address. Two examples of logical units are SYSRDR and SYSPCH. The VSE supervisor uses two control blocks, the logical unit block (LUB) and the
physical unit block (PUB), to map the symbolic name to the real device address.
An entry in the LUB table for a particular logical unit, such as SYSRDR, contains a
pointer to a PUB table entry. The PUB entry contains the address of the reader, X'OOC'. Thus, all programs that read from the logical unit SYSRDR actually read
from the device at address X'OOC'. VSE Support Under eMS 389

On a real VSE machine, logical unit assignments are made dynamically via the ASSGN job statement or the ASSGN operator command. When using CMS/DOS, the CMS ASSGN command performs a similar function.
The ASSGN command in CMS/DOS assigns (or unassigns) a system or program­
mer logical unit to (or from) a virtual I/O device. If a disk is being assigned to a
logical unit, the disk must have been previously accessed via the ACCESS com­
mand. As in VSE, you are not allowed to assign the system residence volume via
the ASSG N command. SYSLOG is the default value assigned to the terminal when SET DOS ON is
issued.
The valid system logical units that can be assigned are: SYSRDR SYSIPT SYSPCH SYSLST SYSLOG SYSIN SYSOUT SYSSLB SYSRLB SYSCAT SYSCLB Other VSE system logical units cannot be assigned. The following VSE system log­
ical units cannot be assigned to a VSE formatted FB-S12 device: SYSIN SYSIPT SYSRDR SYSLST SYSPCH An error message is issued and the command terminated if any of the unsupported
system logical units are specified in the ASSGN command. If SYSIN is specified,
both the SYSIPT and SYSRDR LUB and PUB entries are filled in. If SYSOUT is
specified, both the SYSLST and SYSPCH LUB and PUB entries are filled in.
If you wish to use VSE private relocatable, core image or source statement
libraries, you must assign SYSRLB, SYSCLB or SYSSLB, respectively.
You can assign programmer units SYSOOO through SYS241 with the ASSGN com­
mand. This deviates from VSE where the number of programmer logical units
varies according to the number of partitions. ASSGN creates a VSE Logical Unit Block (LUB) and Physical Unit Block (PUB) entry if the device is unassigned or alters the existing LUB/PUB relationship if the
device is already assigned. ASSGN fills in a one-byte index in the LUB, which
points to the proper PUB entry. This PUB entry contains the channel, unit, and
device type information.
When a system or programmer logical unit is assigned to READER, PUNCH, or PRINTER, the reference is to a spooled unit record device. Card reader and ter­
minal I/O data must not be blocked.
The ASSGN command is also used to ignore (IGN) or unassign (UA) alogical
unit. An I/O operation for a logical unit that is in IGN status is effectively a NOP. When a logical unit is unassigned, its pointer to the PUB table is removed.
Compiler Input/Output Assignments
The compilers supported by CMS/DOS expect input/output to be assigned to the
following devices: 390 VM/SP System Programmer's Guide