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

SPT_WRITEUPDATEX(2) OSS System Calls Reference Manual
application process’s array is written in that area.
For programming information about the WRITEUPDATEX procedure, see the
Enscribe Programmer’s Guide and the Guardian Programmer’s Guide.
Considerations
Buffer use SPT_WRITEUPDATEX() is intended for use with 32-bit
extended addresses. Therefore, the data buffer for
SPT_WRITEUPDATEX() can be either in the caller’s stack
segment or any extended data segment.
I/O counts with unstructured files
Unstructured files are transparently blocked using one of the
four valid block sizes (512, 1024, 2048, or 4096 bytes; 4096 is
the default). This transparent block size, known as BUFFER-
SIZE, is the transfer size used against an unstructured file.
While BUFFERSIZE does not change the maximum unstruc-
tured transfer (4096 bytes), multiple I/O operations might be per-
formed to satisfy a user’s request depending on the BUFFER-
SIZE chosen. For example, if BUFFERSIZE is 512 bytes, and a
request is made to write 4096 bytes, at least eight transfers, each
512 bytes long, will be made. More than eight transfers happen,
in this case, if the requested transfer does not start on a BUF-
FERSIZE boundary.
DP2 performance with unstructured files is best when requested
transfers begin on BUFFERSIZE boundaries and are integral
multiples of BUFFERSIZE.
Because the maximum blocksize for DP2 structured files is also
4096 bytes, this is also the maximum structured transfer size for
DP2.
Deleting locked records
Deleting a locked record implicitly unlocks that record unless
the file is audited, in which case the lock is not removed until the
transaction terminates.
Waited SPT_WRITEUPDATEX() calls
If a waited SPT_WRITEUPDATEX() call is executed, the
count_written parameter indicates the number of bytes actually
written.
Nowait SPT_WRITEUPDATEX() calls
If a nowait SPT_WRITEUPDATEX() call is executed,
count_written has no meaning and can be omitted. The count of
the number of bytes written is obtained through the count-
transferred parameter of the Guardian AWAITIOX procedure
when the I/O completes.
The SPT_WRITEUPDATEX() procedure must finish with a
corresponding call to the Guardian AWAITIOX procedure when
used with a file that is opened nowait. For files audited by the
Transaction Management Facility (TMF), the AWAITIOX pro-
cedure must be called before the SPT_ENDTRANSACTION()
or SPT_ABORTTRANSACTION() function is called.
You should not change the contents of the data buffer between
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