Path: utzoo!mnetor!uunet!husc6!bloom-beacon!athena.mit.edu!tada
From: tada@athena.mit.edu (Michael Zehr)
Newsgroups: comp.os.vms
Subject: Re: INSTALLED IMAGE question
Message-ID: <5077@bloom-beacon.MIT.EDU>
Date: 3 May 88 14:32:01 GMT
References: <12395117720.16.STEINBERGER@KL.SRI.COM>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: tada@athena.mit.edu (Michael Zehr)
Organization: Massachusetts Institute of Technology
Lines: 21
Summary: What about installed data files

In article <12395117720.16.STEINBERGER@KL.SRI.COM> STEINBERGER@KL.SRI.COM (Richard Steinberger) writes:
>
>	When one or more users run an image that is installed, who's Working
>set quota get's debited? [...] [Can popular images reside in memory 
>even though no one may currently be running that image?]

Yes, it is faster, because the file's header is resident so VMS
doesn't have to do a directory lookup to see where the file is on
disk, but i don't think you can force it to remain in memory.  The
large advantage is when two people are using it they use the same
global pages (i.e. takes up less memory, so it pages less so it's
faster).  

Does anyone know how this applies to data files?  I want two processes
to run at the same time, each of them reading data from a file.  I can
install the file /open, but when i try it /shared, it complains (BADHDR
-- an error was discovered in the image header).  The machine is
really thrashing for memory, so any suggestions on how to make the
processes share data pages would be appreciated.

-michael j zehr