Copyright (c) Digital Equipment Corporation 1992. All rights reserved
LAYERED PRODUCT:  VAX PLI                           OP/SYS:  VMS

SOURCE:     Digital Customer Support Center

SYMPTOMS:

The built-in FLUSH subroutine in PL/I doesn't seem to flush the last buffer
when the PUT statement is used but it does when the WRITE statement is used.

ANALYSIS:

This behavior is correct.  For data written with the PUT statement, PL/I
buffers this data in a "stream block".  The $FLUSH system service, called
by the FLUSH() built-in subroutine, flushes only the RMS buffers.  Since
PL/I has not written its stream block using RMS, the missing data is not
in the RMS buffer(s) to be flushed.

In the case of record I/O (WRITE), it manipulates RMS buffers directly and
does not use its own buffering, hence a $FLUSH on a record I/O statement
accurately reflects all I/O done to the file.  This second is more important,
since shared access to files typically happens on record-oriented files (i.e.
relative or indexed sequential) rather than on stream files.

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