IBM System/370 Manual page 81

1. Time-dependent programs being executed on a 7000-series system
or emulated on a Model 65 may not execute properly. Provision
has been made to allow some time-dependent programs to be
emulated correctly (see the appropriate emulator reference
manual for details>.
2. Programs with undetected programming errors give unpredictable
results.
3. If programs that use unsupported features or I/O devices (as
described for each emulator in successive subsections and in
emulator reference manuals> are to be emulated, they must be
modified to conform to the support provided by the specific
emulator program.
The Tape Preprocessor and Tape Postprocessor formatting programs
supplied to Model 165 7000-series emulator users operate as processing
programs and can be executed with any OS control program generated
with the emulator macro specified. The Tape Preprocessor operates
in a program area of 4K bytes plus I/O buffer requirements and accepts
as input seven- and nine-track tape in 7000-series format. It produces
as output spanned variable-length (OS VBS> format data that can be
written on seven- or nine-track tape or on direct access storage.
Input records longer than 32,755 bytes are reblocked, since OS BSAM
cannot handle a physical data block longer than 32K bytes.
The Tape Postprocessor operates in a program area of 5K bytes plus
I/O buffer requirements and performs the reverse of the Tape
Preprocessor. The postprocessor program is useful when a copy of a
data set in OS
vas
and another in 7000 format are required. (The 7000-
series emulator programs accept as input and produce as output both
the formats handled by these two tape formatting programs.>
The tape formatting programs can handle 200, 556, 800, and 1600
BPI densities, mixed density tape volumes, and even, odd, and mixed
parity tapes.
While existing tape files with blocks longer than 32K bytes must
be preprocessed, conversion to
vas
format offers the user the following:
• The ability to emUlate tape data sets on direct access devices
• The ability to share among several concurrently executing emulator
jobs read-only files maintained on direct access devices, such
as 7000 system libraries.
• The ability to process VBS format data sets with both OS and
emulated 7000-series programs. (Note that OS programs must be
written with knowledge of the VBS format of preprocessed tapes.)
• The ability to increase emulator job performance by reblocking
7000-series format tape files with short blocks, assuming that
enough processor storage is available
• The ability to reduce processor storage buffer requirements by
reblocking files with very large blocks
The following subsections discuss the three emulator programs.
They discuss features and I/O device support, Model 165 configuration
requirements., job SUbmission" conversion requirements, and performance.
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