Path: utzoo!utgpu!attcan!uunet!husc6!rutgers!ucsd!ucbvax!NSCVAX.PRINCETON.EDU!dragon
From: dragon@NSCVAX.PRINCETON.EDU (Richard B. Gilbert)
Newsgroups: comp.os.vms
Subject: Multiple-access files in VMS
Message-ID: <8808031757.AA01886@ucbvax.berkeley.edu>
Date: 1 Aug 88 19:12:09 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Reply-To: dragon@NSCVAX.PRINCETON.EDU
Organization: The Internet
Lines: 19


   Mike Temkin writes:
>Does anyone out there know how to make a file multi-accessible (readwise)
>in VMS?  There must be a way since I would think that the help file is
>that way.  Any help is appreciated.

   Sharability is not an attribute of a VMS file.  File sharing is
controlled by the bits in FAB$B_SHR in the File Access Block (FAB) which
are set when a program opens the file.  As soon as a program opens a file
for exclusive access, it is no longer shareable. 

   Any program that opens a file to write to it will almost certainly open
it for exclusive access.  Programs written in high level languages 
sometimes default to exclusive access.  From VAX Fortran, for example, the
OPEN statement must include the keyword SHARED, else the file is opened for
exclusive access, (FAB$B_SHR=FAB$V_NIL).

    See "VAX Record Management Services Reference Manual", Order No. 
AA-Z503B-TE for more than you wanted to know about file sharing. :-)