HP 3000 Manuals HP 3000 Manuals
File Access From Threads
The following is a high-level overview of the file system functionality
available:
* The file system supports thread sharable NM disc files, including
user mapped files and spoolfiles. CM files (tapes, cir,
rio, CM KSAM) are thread private (Thread-Non-Sharable).
Thread-Semi-Sharable terminals and printers are supported.
Thread-Semi-Sharable means that some, but not all, intrinsics can
be called from all threads for these file types.
* PRINT and READX can be used by any thread if $STDIN or $STDLIST is
an AVESTA or Virtual Terminal. They are only supported for the
initial thread, if the terminal is a TMUX Terminal. READ is
supported for the initial thread only for all terminal types.
* Only the initial thread can open Thread-Non-Sharable or
Thread-Semi-Sharable files as system files. Only the initial
thread can re-open system files if the system files are printers
or terminals. However, HPFDUPLICATE allows each thread to get
their own file descriptor for a system file.
* FCHECK(filenum) returns the last error that the calling thread
incurred on the file if that error is also the last file system
error for the calling thread.
* FLOCK bahaves as an advisory lock outside task boundries; if one
thread in a task has a file FLOCKed, all other threads block if
they call a file system intrinsic on the file.
* For IOWAIT, only the thread that opened the file for NOWAIT IO can
call IOWAIT for that file, and only the thread that opened the
file with NOWAIT can call any IO intrinsics on the file.