avg % of SGA allocated to buffer cache

From: kyle Hailey <kylelf_at_gmail.com>
Date: Fri, 25 Oct 2013 16:45:55 -0700
Message-ID: <CADsdiQhwV0cEeE9t5JNNUukq-=v0Eqn9we3KM4AUNbkWO1ysOQ_at_mail.gmail.com>

Has one seen, or does anyone have, data on what the average size of buffer cache is across Oracle databases? and/or average % of SGA allocated to buffer cache.
One reason I ask, among several, is that pluggable databases save about  300-400MB per instance going from non-PDB to PDB. Thus Oracle claims they can go from 50 instances on a 20GB RAM host to 250 with PDB.
First I'd be surprised at anyone running 50 Oracle instances on 20GB of RAM second I find it hard to fathom running 250 PDB on 20GB of RAM meaning that they'd all have a few MB of buffer cache available each at best.

If PDB option is $17,500 it might be more cost effective to either add more memory to the machine or add more cache to the back end array serving I/O.

Musing on configuration options ...

  • Kyle
Received on Sat Oct 26 2013 - 01:45:55 CEST

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