Subject: RE: One lock per resource per person?

From: "Chris Kaler (Exchange)" <[email-masked]>
Date: Tue, 19 Oct 1999 11:51:01 -0700

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
Sent: Friday, October 15, 1999 12:32 PM
To: [email-masked]
Subject: Re: One lock per resource per person?

<ja>
A principal can only have one lock on a resource. If the lock is exclusive,
then
there can only be one. If the lock is shared, then getting another shared
lock
would not give owning principal any further capability. I don't have the
spec if
front of me, but I believe this is spelled out.
</ja>

<ck/> I think this is too restrictive.  Using SCC systems today, I can
      create multiple shared locks against the same resource.  In
      general you can do this by "checking it out" multiple times, but
      the basic notion is that I may be engaged in parallel activities
      at my client even though I am the same principal.

---

From: "Geoffrey M. Clemm" <[email-masked]>
Date: Tue, 19 Oct 1999 22:57:27 -0400

From: "Chris Kaler (Exchange)" <[email-masked]>

   <ck/> Using SCC systems today, I can

It's very important to distinguish "multiple checkouts" from "shared
locks".  Multiple checkouts are safe and do not suffer from any lost
update problem.  Shared write locks are not safe, and you are
susceptible to getting your update's trashed by anyone else that
shares that lock.

Cheers,
Geoff