Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!mnetor!yetti!geac!daveb
From: daveb@geac.UUCP (Dave Brown)
Newsgroups: comp.unix.wizards
Subject: Re: UNIX Facilities for Interpreters - (nf)
Message-ID: <831@geac.UUCP>
Date: Wed, 24-Jun-87 10:19:58 EDT
Article-I.D.: geac.831
Posted: Wed Jun 24 10:19:58 1987
Date-Received: Thu, 25-Jun-87 07:15:56 EDT
References: <540@iscuva.UUCP> <8300006@iaoobelix.UUCP> <680@nu3b2.UUCP> <684@nu3b2.UUCP> <7168@mimsy.UUCP>
Reply-To: daveb@geac.UUCP (Dave Brown)
Organization: The little blue rock next to that twinkly star.
Lines: 26
Summary: mapped files and concurrency control

Bob Alexander asked:
>Can the file still be used normally?

  Maybe even better...

  On Multics I once saw a demonstration (done by Paul Stachour, if
memory serves), of two persons editing the same place in the same
file at the same time...  the mapping mechanism searialized the
accesses so they didn't mash the same character at the same time, 
and Emacs laboured mightily to keep its screens updated in the face
of the file changing *under* it.
  It was impressive, but not directly useful: it only worked because
the two people were in the same office discussing the changes on a
secondary channel (voice).. But on a TP system, it would be a joy!
Instead of complex locks & commits on disk blocks, you have them
on memory.
  Of course, this opens a whole new pandora's box of implementation
problems. (:-))

	--dave

-- 
Computer Science  | David (Collier-) Brown 
loses its memory  | Geac Computers International Inc.
every 6 months    | 350 Steelcase Road,Markham, Ontario,
           -me.   | CANADA, L3R 1B3 (416) 475-0525 x3279