FLASH -flash count overlay use
This information is contained in the VSPIBLOK for a virtual printer. When the file is closed, the information is contained in the first DASD
buffer.
Input file processing is similar to output file processing, except for
the open and close functions, and the analysis of CCW commands and the
direction of data movement. Many common routines are utilized to locate
and verify CCWs, obtain buffer space, and to move the spooling data.
The difference in the open function is that instead of creating a new it is necessary to locate a reader file that already exists in the
system. To do this, -the open subroutine scans the SFBLOKs chained from the anchor, READERS, to find a file with an owner userid that matches that of the caller and is not in hold status. If a file is not found, a
unit check or intervention required condition is reflected to the
virtual machine; otherwise, its SFBLOK is chained to the control block
for the reader and the channel program is interpreted in the same manner
as for an output file.
After the input file is exhausted, a unit exception is reflected to
the user machine, unless the user has requested either continuous
spooling or that an EOF not be reflected. With continuous spooling, the
unit exception is not reflected until the last file for that virtual
machine is processed. If NOEOF is specified, the simUlation terminates
with a unit check or intervention-required condition (similar to what
happens if the EOF button on a real reader is not pushed).
In
unless
saved.
either case, the input file is then deleted from the system, the user has specifically requested that his input files be
If the file is saved, it can be re-read any number of times.
Support of virtual console I/O for both the virtual
is provided as an option for the VM/370 spooling
support fulfills the following requirements: machine and VM/370 capabilities. This • Provides hardcopy support for CMS Batch Facility virtual machines. • Provides hardcopy support for display devices used as system or
virtual machine consoles. • Allows disconnected virtual machines to spool virtual console output, CP commands and system resources to disk instead of losing the
output. • Improves the performance of virtual machines that currently produce a
large amount of console output. Whenever a SIO is issued to a virtual machine console, the virtual
console manager (DMKVCN) determines if the spooling option is active.
If it is, control is passed to the virtual spooling manager at DMKVSPBP to insert the data into a spool file buffer. While console spooling
utilizes, basically, the same code as printer spooling, the following
exceptions are made: CP Introduction 1-141

• A skip to channel 1 CCW is inserted after every 60 lines of output. • The operator's virtual console spool buffer is written out after
every 16 lines of output. • The virtual spool buffer is written out to the allocated spool device
when the first CCW is placed in that virtual buffer. The linkage area
of the virtual spool buffer takes the fora of a CLOSE file to allow
checkpoint (DMKCKP) to recover the active spool file in the event of
a shutdown because of system failure. If data in the virtual buffer
has not yet been written to the spool device, it will not be recovered. To maintain a pseudo closed file status for console spool files, DMKSPL now assigns spool identifications to all output spool files
where they are first queued.
A virtual system reset, device reset, or IPL close the
virtual console spool file. The LOGOFF, FORCE, or DETACH of virtual
console commands does close the virtual console spool file. The SHUTDOWN command does close the operator's console spool file. If
the SHUTDOWN co •• and is issued by a Class A user other than the
operator, the console spool file for both the user and operator is
closed.
The inclusion of the spool file tag record in a virtual console spool
file is processed by DMKVSP and DMKSPL as described for printer spool
files in "Output File Processing" under "Virtual Spooling Manager." REAL SPOOLING MANAGER (DMKRSP) The real spooling manager operates the real unit record devices that are
attached to the system and that are used to transcribe input data into
reader spool files and user output spool files onto the real printers
and punches. The executive opti.izes the use of main storage and the
processor rather than running the system unit record devices at their
rated speeds. DASD input files are not double-buffered
except for a 3800 printer, and under periods of peak load, input and
output devices tend to run in bursts. However, command chaining is used
for all unit record channel programs so that the devices are running at
their .aximum speed with a mini.um of interruptions.
Both the input and output operations of DMKRSP are interruption driven.
Thus, DMKRSP does not process unless an internally or externally
generated not-ready to ready device end interruption occurs. External
interruptions are generated by the hardware in the nor.al manner, while
internal, "pseudo interruptions," are generated by the software when an
output file has been queued on the real printer or punch file chain, or
when the operator issues a START co.mand to a drained device. Upon receipt of the initial device end for a printer or punch, DMKBSP searches the appropriate file chain for the SFBLOK of a file whose class
.atches that of the device that was aade ready. If FLASH is specified
for a 3800 printer, the flash overlay naae must also match. When the SFBLOK is located (provided the file is not in a hold status), it is
1-142 IBM VM/370 System Logic and Problem Deteraination--Volu.e 1