Re: Optimistic or Pessimistic Concurrency Control?
Date: Sun, 10 Sep 2000 03:57:09 GMT
Message-ID: <8pf0qd$9vi$1_at_nnrp1.deja.com>
In article <D8wu5.1288$M37.88812_at_bgtnsc07-news.ops.worldnet.att.net>,
"Tony" <tony_at_my.isp.net> wrote:
> I thought locking WAS a (read, is THE) pessimistic technique.
>
> Tony
>
> "Joe Trubisz" <trubisz_at_cs.sunysb.edu> wrote in message
> news:39b42c04_1_at_dilbert.ic.sunysb.edu...
> > Tony (tony_at_my.isp.net) wrote:
> > : Which is decidedly 'better' (most often used in current commercial
> > : databases) optimistic or pessimistic concurrency control and why?
> > : Tony
> >
> > Neither. Most use two-phase locking. Some offer optimistic, but
> > it's rarely used.
> >
> > Joe Trubisz
> > Dept. of Computer Science
> > SUNY Stony Brook
> > Stony Brook, NY 11794
>
The only two-phase locking I am familiar with is on distributed
queries. Oracle is the most wide spread commercial database and it
does not lock rows until you actually issue an update against the row
unless you request a select for update. According to its manuals it
uses an optomistic locking scheme.
-- Mark D. Powell -- The only advice that counts is the advice that you follow so follow your own advice -- Sent via Deja.com http://www.deja.com/ Before you buy.Received on Sun Sep 10 2000 - 05:57:09 CEST