Re: Pluggable database in 12C

From: Noons <>
Date: Thu, 25 Oct 2012 21:33:10 +1100
Message-ID: <k6b4h6$5rg$>

Mark D Powell wrote,on my timestamp of 25/10/2012 5:16 AM:

>>> single set of LGWR processes will be the Achiles' heel of the 'pluggable
>>> database' revolution <<
> Won't that really depend on how your containers are allocated? Ignorning RAC
> you have one instance, one database, one log now. If you split the database
> schema into their own containers do you really have any more logging activity
> to be handled that what the log writer process is currently handling? In
> other words is this really an issue now?

It is if one is consolidating, which is the whole reason for the PDBs. Ie, not running one application per instance. You run one per schema/PDB. And if you add sufficient load of them to a single instance's redo logs, you got a serious contention problem right there. MSSQL doesn't, because it uses discrete logs for each PDB. Let's hope Oracle keeps it that way.

> Now if you have 10 RAC databases on one server like we do (mostly vendor
> products) that for security and upgrade reasons need to be separate if we put
> them each into a PDB we would be increasing the activty of the one 12c
> instance about 4X so them maybe the logging would be an issue. But I do not
> consider this type of consolidation to be the likely norm any time soon.

Surprisingly, it is. Not necessarily with RAC, mind you. In fact it's beginning to look more and more like 12c PDB is just an extension of the "single-node RAC" trials of 3-4 years ago. Received on Thu Oct 25 2012 - 12:33:10 CEST

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