3800 Printing Subsystem Support The 3800 printer is supported with all its functions as a dedicated
device. It has limited functional support when it is used as a spooling devicee Following is a list of features of the 3800 printer: I. PORMS CONTROL peraits the user to select the amount of vertical space I between printed lines. Lines can be vertically spaced at 6, 8, or 12 I lines per inch. Different spacings can also be mixed on the same I page. I • PORMS OVERLAY permits photographing of predefined data (forms) on one I or aore pages. The 3800 printer supports the creation of a form on a I page and the i.aediate printing of data on that form. I • PREDEFINED CHARACTER SETS permit the user to select previously I designated character sets that contain up to 64 characters each. I Different character sets provide varied character types, sizes, and I horizontal spacings between the characters. The 3800 supports the I simultaneous use of two character sets and optionally supports the I use of two additional character sets. The user can mix characters I froa the different character sets on a single page. Characters are I referenced within the 3800 through the use of translate tables. Up I to four translate tables may be loaded at anyone time. t • CHARACTER SET MODIPICATION permits user modification and extension of I character sets. I • COpy MODIFICATION per.its printing of predefined data (for example, t the same header on each page) or the suppression of printing I for selected data. I • MULTIPLE COPIES permits numerous copies of files and data sets to be I printed without the use of multiple-ply paper. Numerous copies of a I single 3800 buffer can also be printed.
The values that control feature selection and printing on the 3800 are stored in tables and aodules. Through use of the CP co.mands VM/310 can display the syabolic names of the translate tables and modules in
addition to the syabolic naae of the library where they are stored. Before printing a spool file, VM/310 initializes the 3800 by loading
it with the translate tables that control feature selection and
printing. VM/310 provides a capability to purge spool files that cause
load errors, which occur when a name is specified that does not match the specified image library. If PURGE is specified, all spool files
causing 3800 load errors will be purged. Otherwise, the spool file will
be held.
DEDICATED 3800 PRINTER SUPPORT YM/310 allows virtual aachines, including virtual V8/370, to attach the 3800 printer as a dedicated I/O device. When attached, the full
capability of the 3800 is available to the virtual machine. All of the
functions previously described are available when the 3800 is used as a
dedicated device, provided the device is specified in the RDEVICE macro
instruction at system generation. See the 26 VM/370 Operator's Guide

Performance Options VM/370 offers the following performance options to enhance the operating
efficiency of one or aore virtual machines. This enhancement is
nor. ally at the expense of the performance of other virtual machines. In certain instances, enhancements to a specific virtual machine (or
aultiple virtual machines) are detrimental to the operating efficiency
of other virtual The performance options are: • Virtual machine assist • VM/370 Extended Control-Program Support • Reserved page frames • Favored execution • Virtual=real • Locked pages • Priority • Affinity in an attached processor environment You can dynaMically assign or withdraw any of these options except
for the virtual=real option (it can only be dynamically withdrawn) fro.
virtual machine users during system operations. You can assign to one
virtual machine a "mix" of performance options, or the options may be
assigned to separate virtual machines. Efficient use of these options
depends upon the characteristics of the program applications; the nUMber, size, and complexity of the virtual machines being run; and the
size, I/O configuration, and CPU model of the real computer being used.
In addition to using these performance options, you can also use the SET PRIORITY command to change a virtual machine's execution priority
and, thereby, change its performance. For example, you could assign the following mix of One virtual machine: Reserved Pages=10 Favored Execution=80% Virtual Machine Assist
Another virtual machine: Virtual=Real priority=1
A third virtual machine:
Locked Pages=2 The favored execution (with percentage value specified), VIRT=REAL, and the reserved page option are unique in that each option cannot be
applied to multiple virtual machines at the same time. However, no.such
restrictions apply to the locked pages, virtual machine assist, VM/370 Extended Control-Program Support, priority, or favored execution
(without the percentage value) options; they can be applied' to multiple virtual machines. RESERVED PAGE FRAMES OPTION The CP paging routine uses chained lists of available and pageable pages
to control real storage use. CP assigns pages for users from the
available list, which it replenishes from the pageable list.
Section 2. Initiating VM/370 Operation 27