@@
Tape Dummy File         TA10010n


A. Overview

Function:  The tape dummy file is used (by Vax VMS systems) as a means
to take exclusive use of a tape drive.

Details:  The Vax VMS system's elegant design for tapes does not allow
a sub-process to take exclusive use of a tape drive.  The parent
process (i.e. AIPS) can still perform a rewind in the middle of a job
which is writing on the tape!  In order to avoid this, all open
operations on tapes also open exclusive a disk file called TA10010n,
where n is the tape drive number.  This need be done only on Vax VMS
sytems and is hidden away in the Z routines.

Name:  The files are named TA10010n, where n is the tape drive number.
They are permanent files, but need not contain any data.  They must be 
created during system installation (on Vax VMS systems anyway).


B. File structure


     The file contains no data and need not even have any records.



C. Usage notes


     These files are accessed by ZOPEN and ZCLOSE on Vax VMS systems
and should not be accessed by any other programs.
