Open System Services System Calls Reference Manual (G06.28+, H06.05+)

SPT_WRITEUPDATEX(2) OSS System Calls Reference Manual
If the buffer or count transferred is in a selectable extended data
segment, the segment must be in use at the time of the call. Flat
segments allocated by a process are always accessible to the
process.
Use on files opened for nowait I/O
— If the buffer is in an extended data segment, you cannot
deallocate or reduce the size of the extended data seg-
ment before the I/O completes with a call to the Guar-
dian AWAITIOX procedure or is canceled by a call to
the SPT_CANCEL() function or the Guardian CAN-
CELREQ procedure.
— You must not modify the buffer before the I/O completes
with a call to AWAITIOX. This also applies to other
processes that might be sharing the segment. It is the
application’s responsibility to ensure this.
— If you initiated the I/O with
SPT_WRITEUPDATEX(), the I/O must be completed
with a call to the Guardian AWAITIOX procedure.
— The extended segment containing the buffer need not be
in use at the time of the call to AWAITIOX.
— Nowait I/O initiated with SPT_WRITEUPDATEX()
can be canceled with a call to the SPT_CANCEL()
function or the Guardian CANCELREQ procedure. The
I/O is canceled if the file is closed before the I/O com-
pletes or AWAITIOX is called with a positive time limit
and specific file number and the request times out.
Bounds checking
If the extended address of the buffer is odd, bounds checking
rounds the address to the next lower word boundary and checks
an extra byte as well. The odd address is used for the transfer.
Magnetic Tape Considerations
Supported equipment
SPT_WRITEUPDATEX() is permitted only on the 3202 Con-
troller for the 5103 or 5104 Tape Drives. This function is not
supported on any other controller/tape drive combination.
SPT_WRITEUPDATEX() is specifically not permitted on the
following controller/tape drive pairs:
— 3206 Controller and the 5106 Tri-Density Tape Drive
— 3207 Controller and the 5103 & 5104 Tape Drives
— 3208 Controller and the 5130 & 5131 Tape Drives
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