Re: Multiple RBS tablespaces

Ooops. I should have slowed down. I see the issue is one of separate rollback TABLESPACES. Mea culpa.

The only possible need for multiple rollback tablespaces is if you've got a hybrid system -lots of OLTP on a daily basis, and huge great batch transactions at, say, Month-end (or overnight). That situation requires differently-sized and different numbers of segments (respectively, lots of small ones, and a few huge ones). You really don't want your big batch transactions hitting the small segments (because it will force them to wrap and grow big, and hence slows everything down). So you need a mechanism for directing transactions to the right tablespace -and if you were to offline the 'small tablespace' when you start your big bulky transaction, it can ONLY use the 'big tablespace' rollback segments.

Likewise, you don't want your OLTP stuff getting into the few big segments -because that *would* introduce segment header contention. So, for normal daily activity, you offline the the 'big tablespace', and your OLTP transactions have no choice but to use the small segments.

Of course, if you have access to the source code, you can achieve this direction of transactions to an appropriate rollback segment without fiddling at the tablespace level. Otherwise, it's a fairly standard technique.

And if you don't have a hybrid system requiring different sorts of rollback segment, then I see no need for different rollback tablespaces.

Regards (and sorry for reading it wrong first time) HJR

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"Howard J. Rogers" <howardjr_at_www.com> wrote in message
news:3a148522_at_news.iprimus.com.au...


> The issue is not one of I/O contention, but of segment header

 contention -if


> you've got 100 people trying to do OLTP-type transactions, and they're all

> fighting over access to the one rollback segment, you can expect Oracle to

> be forced to have to queue them up behind each other.

>

> The usual rule of thumb is that to get round this contention issue, there

> should be 1 rollback segment per every 4 concurrent transactions.  And it

> really won't matter too much if they are all sitting on the one disk:

> contention for the segment header would make i/o contention look like a

> children's picnic.

>

> Regards

> HJR

> --

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> Opinions expressed are my own, and not those of Oracle Corporation

> Oracle DBA Resources:               http://www.geocities.com/howardjr2000

> --------------------------------------------------------------------------

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>

>

> <gorgos_at_my-deja.com> wrote in message news:8v0la7$705$1_at_nnrp1.deja.com...

> > Hello again,

> > a colleague of mine was suggesting that multiple rollback segment

> > tablespaces was good.  If the tablespaces are on seperate disks, I can

> > understand that IO contention will be reduced, but if they're on the

> > same disk and don't see the benefit.  Am I missing the point here ??

> >

> > Thanks

> >

> >

> > Sent via Deja.com http://www.deja.com/

> > Before you buy.

>

>