Re: Concurrency in an RDB

From: NENASHI, Tegiri <tnmail42_at_gmail.com>
Date: Thu, 14 Dec 2006 18:38:24 +0100 (CET)
Message-ID: <Xns989980BE3BB7Easdgba@194.177.96.26>

"Cimode" <cimode_at_hotmail.com> wrote in
news:1166113032.469596.104340_at_n67g2000cwd.googlegroups.com:

>
> Christopher Browne a écrit :
>

>> In an attempt to throw the authorities off his trail, Bob Badour
>> <bbadour

> @pei.sympatico.ca> transmitted:

>> > Transactions may acquire and release many locks over the duration
>> > of the transaction which may be orders of magnitude longer than the
>> > duration of any lock.
>>
>> Are you sure they ought to release them?
>>

> There is NO direct relationship between locks and deadlocks.

It is not true. Locks can cause dead locks:

Process1: ->lock Resource1--work 2 minutes -> lock Resource2 -> wait for Process2 ->dead lock
Process2: ->lock Resource2--work 1 minute -> lock Resource1 -> wait for Process1 ->dead lock

>
> Behavior of locks is purely technology-and implementation-dependent.
> It is often a consequence of the RAM/disk swapping methodology used.
> Deadlock are mainly a result of strong contention preventing easy lock
> or metadata swapping...
>
>
Received on Thu Dec 14 2006 - 11:38:24 CST