Re: enqueue timeouts ?

In article <eaGN4.280$ac5.6562_at_news11-gui.server.ntli.net>,   "Guy Fullalove" <nospam_at_127.0.0.1> wrote:
> Oracle 7.3.4 on Solaris 2.6
>
> Can anyone tell me what enqueue timeouts are, if they are a problem,
 and how
> to prevent them?
>
> Thanks
>
> --
> Guy Fullalove
> (guy.fullalove_at_which.net)
>

Enqueues are basically a lock on a resouce. The exact manner in which they are accomplished varies by OS.

A timeouts is an indication that a process could not get a resource it wanted and had to go into a wait state. Note that enqueues are not first in first out but are given out as available so if process A gets a resource and B asks for it while it is inuse the B goes into a wait. A releases it and C asks for it. C gets it and B comes out of its wait and requests it again. C has the resource so B waits again.

Enqueue waits can be caused by:

--  1) contention for specific row
--  2) tbl locks caused by unindexed FK
--  3) ST lock contention on non-temporary temp tablespace
--  4) no available transaction slot in block [initrans parameter]

--
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.