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BLOCKTAP.HELPCMD.D1
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BLOCKTAP.HELPCMD.D1
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BLOCKTAP Nucles Extension
Trap TAPEIO calls and change the blocksize to 32k (approx). This was written
expressly to improve the functions of VMFPLC2 and TAPE. There are sequences of
I/O operations which are probably NOT handled correctly by this routine but it
should work correctly for all sequences generated by VMFPLC2 and TAPE. Tapes
created withOUT BLOCKTAP will be readable with BLOCKTAP ON.
+----------+------------------------------------------------------------------+
| BLOCKTAP | ON|OFF|Q|CLOSE [(options...[)]] |
| | options: |
| | BLOCK|NOBLOCK TYPE|NOTYPE TAP1|TAPi|181|cuu |
| | Default Options: TAP1 BLOCK TYPE |
+----------+------------------------------------------------------------------+
where:
ON installs the nucleus extension (unless already installed) and turns it
ON for the specified (or defaulted) device.
OFF turns it OFF for the specified (or defaulted) device and removes the
nucleus extension if no devices are still ON. It performs the CLOSE
and Q functions before extracting itself.
CLOSE performs any necessary tape operations to insure that the physical
tape reflects the commands which have been buffered. The buffer is
empty after this operation. It performs the Q function after closing.
Q gives statistics for output operations. Included are the number of
bytes, gaps and tape marks written. Also, the length of tape written
in feet. (Both virtual (what would have been written without BLOCKTAP)
and real (what was actually written to the tape) are reported.
Options:
TAPn 18n specifies the symbolic tape identification (TAPn) or the actual device
address of the tape to be read from or written to, where n is 0 to F,
corresponding to devices (cuu) 180-187 and 288-28F. The default is
TAP1 or 181. The unit specified by cuu must previously have been
attached to your CMS virtual machine before any tape I/O operation can
be attempted.
NOBLOCK specifies that the output tape blocksize is NOT to be altered. This
option will optimize tape movement and eliminate the extra gaps
produced by superfluous tape marks and subsequent re-positioning of
the tape. Tapes created with this option will be readable without
BLOCKTAP.
Options BLOCK and NOBLOCK may be specified ONLY with the ON function.
TYPE specifies that statistics are to be given on the CLOSE and OFF
functions.
NOTYPE specifies that statistics are NOT to be given on the CLOSE and OFF
functions. The confirmation messages on the ON function are also
suppressed. This option has NO effect on the Q function.
The TYPE/NOTYPE setting is preserved for the specified device until
changed (by specifying the opposite setting).
This command installs a Nucleus Extension for the TAPEIO function. The nucleus
extension buffers I/O requests and causes the tape to be written in standard OS
VariableBlocked format. Each record in this format is one TAPEIO request. A
block is written to tape ONLY when addition of data to it would cause it to
exceed 32760 bytes. It is also written if an ERG, SENSE, REW or RUN command is
given.
Note that WTM, BSF, FSR and BSR commands are buffered. This saves tape when the
"standard" CMS command sequence of "write the file, WTM, WTM, BSF, BSF" is
issued over and over again ... because the superfluous tape marks are NOT
written.
The user must NOT re-position the tape with any CP commands while BLOCKTAP is
ON because the last few commands are probably still in the buffer and were NOT
written to the tape!!!
NO warrantee of ANY kind is either expressed or implied by the author or
Brigham Young University.
Author: Steven C. Howes Brigham Young University
Version: 1
Date: 11 May 1987