Re: high "gc busy buffer"

From: Jonathan Lewis <jonathan_at_jlcomp.demon.co.uk>
Date: Thu, 13 Jan 2011 10:14:47 -0000
Message-ID: <M-KdnUDuQs4FTbPQnZ2dnUVZ8gGdnZ2d_at_bt.com>

"charles" <dshproperty_at_gmail.com> wrote in message news:ecd9f8b4-0bcc-497b-9e49-9a0f146159a2_at_i17g2000vbq.googlegroups.com...

> thanks very much for your help. No wonder i set pctfree=99, and the
> situation get worse. Yes, i forget, there is select, insert, update,
> delete with 5,000 people sign on at the same time.
>
> I will try to use one node tomorrow, but not sure CPU will be able to
> handle that.
>
> If i do not want to use single hash clustered table, as i am not sure
> that table will stay small, i should create an reverse key index for
> this, am I right?

Is this table something like a 'current sessions' table ? What is the primary key - constantly increasing number, session id, GUID ...
How big is the table likely to grow ?

If the table is going to stay small and you have lots of inserts and deletes then
a) the index will be small
b) all the index entries will be packed into a small number of blocks

Reverse key won't help. If you are licensed for the partitioning option then a hash partitioned IOT with (say) 512 or 1024 partitions might keep the contention within acceptable limits. But since I'm only guessing what the table is for and how it will be used that's not a very solid suggestion.

-- 
Regards

Jonathan Lewis
http://jonathanlewis.wordpress.com

Received on Thu Jan 13 2011 - 04:14:47 CST