When you release a disk from your virtual machine, any assignments made to that disk are unassigned. You can find out the current assignments for system and programmer logical units with the LISTIO command, which lists all the system or
programmer logical units, even those that are unassigned:
listio
To list only currently assigned units, enter:
listio a
To find out the current assignment of one specific unit, for example SY5100, enter:
listio sys100 With the EXEC option of the LISTIO command, you can create a disk
file containing the list of assignments. The $LI5TIO EXEC that is
created contains two EXEC numeric variables, &1 and &2, for each unit
listed. For example, if you entered the command: listio sys081 (exec
then the file $LISTIO EXEC may contain the record:
&1 &2 SYS081 PRINTER When you use the STAT option, LISTIO lists, for disk devices, whether
the disk is read-only or read/write; for example:
listio sys100 SYS100 B R/i
indicates that SYS100 is assigned to the B-disk, which is a read/write
disk. You can cancel all current assignments by leaving the eMS/DOS environment and then re-entering it:
set dos off
set dos on VIRTUAL MACHINE ASSIGNMENTS When you assign a physical device type to a system or programmer logical
unit, CMS relates the device to your virtual machine configuration; you
receive an error message if you try to assign a logical unit to a device
not in your configuration. For example, if you are using the 15SGB command to assign a logical unit to a disk file, you must specify the
access mode letter of the disk. If the disk is not accessed, the ISSGB command fails.
For another example, if you issue: assgn syspch punch
the punch specified is your own virtual machine card punch. The actual
destination of punched output then depends on the spooling
characteristics of the punch; if it is spooled to another user or to *,
then no real cards are punched, but virtual card images are placed in
158 IBM VM/370 CMS User's Guide

the virtual reader of the destination userid, which may be another
virtual machine or your own. eMS supports only one reader, one punch, and one printer; you cannot make any assignments for multiple output devices in CMS/DOS. When you
make an assignment for a logical unit that has already been assigned, it
replaces the current assignment.
Using the DLBL Command Use the DLBL command to supply CMS/DOS with specific file identification
information for a disk file that is going to be used for input or
output. For any DLBL command you issue, you must previously have issued
an ASSGN command for the disk, specifying a sjstem or programmer logical
unit. The basic relationship is:
assgn SYSxxx mode dlbl filename mode DSN 1 (SYSxxx Both the SYSxxx and the mode values must match on the ASSGN and DLEL
commands; the disk on which the file resides must be accessed at mode.
The filename on the DLBL command line, called a ddname in CMS/DOS, corresponds to the symbolic name for a file in a program. If you want to
reference a private DOS library, you must use one of the following
ddnames: 12g.!£g! Y.!!it SYSCLB SYSRLB SYSSLB IJSYSCL IJSYSRL IJSYSSL ENTERING FILE IDENTIFICATIONS When you issue the DLBL command you must identify the file, by file-id
(for a DOS file) or by file identifier (for a CftS file). The keywords DSN and CMS indicate whether it is a DOS file or a CMS file,
respectively.
If the file is a DOS file residing on a DOS disk, you can enter the
DLBL command in one of two ways. For exam FIe, for a file named TEST.INPUT you could enter either:
assgn sys101 d
dlbl infile d dsn test input (sys101 -- or
assgn sys101 d
dlbl infile d dsn 1 (sys101 ENTER DATA SET NAME: test. input
For any DOS file with a file-id that contains embedded blanks or
hyphens, you must use the "DSN 1" form. Section 9. Developing DOS Programs Under CMS 159