IMAGE LIB loads the new or changed text files created by GENIMAGE into vir­
tual storage. When all the files are loaded, DIAGNOSE Code X'74' is invoked to
save these files as a named system.
IMAGEMOD makes selective modifications to an existing 3800 named system
without completely regenerating the named system. While IMAGELIB creates a
new named system each time it is invoked, IMAGEMOD allows users to add,
delete, replace, and list members of a 3800 named system. IMAGEMOD uses
DIAGNOSE X'74' to load and save the named system.
See the VM I SP Planning Guide and Reference for more information on
IMAGELIB, GENIMAGE and IMAGEMOD.
Storing and Loading Control Tables
Recovering from I/O Errors
As part of VM/SP support of the 3800 printer, character arrangement tables, copy
modifications, graphic modifications, and FCBs are stored in a named system.
Prior to printing a spool file, the VM/SP operator specifies a named system on the
IMAGE parameter of the START command. The control tables specified for the
file (via the SPOOL and CHANGE commands) are loaded into the 3800 from that
named system and the file is printed.
The NAME3800 macro instruction establishes the named system at system gener­
ation. See the VM I SP Planning Guide and Reference for further information.
Because the actual printing of lines on the page is slower than the output of lines
from the processor, spool files are placed into a delayed purge queue to await print­
ing by the 3800. Only when the maximum number of files are in the queue will the
first one actually be purged. The size of the queue can be specified at system gen­
eration time via the DPMSIZE parameter on the RDEVICE macro instruction.
DPMSIZE can have a maximum value of nine.
Because spool files are queued, the BACKSP AC command may be used for the 3800 printer to restore pages that are lost when an 110 error occurs. In addition,
the operator may specify the EOF parameter, which indicates that backspacing
should begin at the end of the file and continue for the number of pages specified.
See the VM I SP Operator's Guide for more information on the BACKSP AC com­
mand.
Displaying Printer Control Information
The QUERY command enables G-, B-, and D-privilege users to display the names
of the character arrangement table, copy modification, and FCB currently in effect
for a spool file or a virtual printer. In addition, the VM/SP operator can use the
QUERY command to determine the image library used and the forms loaded on a
real 3800. See the VMISP Operator's Guide for details on the QUERY command.
Using the 3800 Printer as a Virtual Spooling Device
VM/SP enables a user to create printer spool files on a virtual 3800 printer defined
for his virtual machine. VM/SP provides full support for the copy modifications,
forms overlay, character modifications, and multiple copy features. In addition,
IBM 3800 Printing Subsystem 297

when the 3800 is defined as a virtual spooling device, the user can specify that up
to four different Writable Character Generation Modules (WCGM's) are available
for defining characters to print on a line or page. Each WCqM holds 64 charac­
ters. Finally, the user can vary the vertical spacing of lines o'n· a page.
VM/SP makes these 3800 features available both to CMS users and to virtual
machines running an operating system with full 3800 support. When a virtual
machine running an operating system with full 3800 support issues commands that
generate 3800 load commands, the virtual machine operating system passes these
load commands and their associated data to CP. CP includes these load commands
in the virtual spool file.
Four commands and macros make it possible for CMS users to load a virtual 3800 printer and to print virtual 3800 spool files. The SETPRT command and parame­
ters on the PRINTL macro, and PRINT and FILEDEF commands make it possible
to use the features of a 3800 printer.
Parameters on the CP START command allow the VM/SP operator to control the
printing of virtual 3800 spool files. The QUERY command enables a user to
determine the characteristics of his virtual 3800 printer or spool file.
Defining a Virtual 3800 Printer
To use the features of the 3800 printer as a virtual spooling device, the installation
or user must define a virtual 3800 for the user's virtual machine. The class G
DEFINE command enables a user to specify virtual 3800 characteristics, including
how many WCGMs the virtual printer has, and whether or not CP will reflect all
data checks to the virtual machine. (See the VM / SP CP Command Reference for
General Users for details on the DEFINE command.)
The SPOOL control statement of the DIRECT command allows an installation to
define a virtual 3800 in a user's directory. (See the VM/SP Planning Guide and
Reference for details on the SPOOL control statement.)
Loading the Virtual 3800 and Printing Virtual 3800 Spool Files
The CMS SETPRT command allows a CMS user to include 3800 control informa­
tion at the beginning of a spool file. When the file prints on a real 3800, the real
printer uses this control information to determine which character sets, copy mod­
ifications, and FCB to load and which copies to print with the forms overlay. The
SETPRT command also allows a user to specify copy groups and the number of
copies to print. (See the VM / SP CMS Command and Macro Reference for details
on the SETPR T command.) Once the SETPR T command has been issued, CMS allows a user to select the
character set used to print each line of a virtual 3800 spool file. The TRC option
of the CMS PRINT command and the PRINTL macro indicates that each line in
the file has a TRC (Table Reference Character) as the first byte of data. The TRC
bytes correspond to the order in which character sets have been loaded by the
SETPRT command. When the file prints on the real 3800 printer, the value of the
TRC byte determines which character set the 3800 selects to print each line.
For CMS users running OS programs, coding the OPTCD J parameter of the
FILEDEF command indicates to the QSAM PUT macro and the BSAM WRITE
macro that each output line contains a TRC byte.
298 VM/SP System Programmer's Guide "