PaulB (8/13/2009)
Bruce W Cassidy (8/13/2009)
You can, of course, create multiple Oracle instances. There used to be a great deal of overhead in doing this, but with modern versions of Oracle that's far lower. The only real overhead is in the amount of system database area per instance.Unfortunately statement above does not reflects reality.
Multiple instances DO add a lot of overhead no matter Ora version, anything in between 17 to 30 daemons running per instance plus all SGA/PGA instance specific memory segments.
[font="Verdana"]Yes and no. It's true you get a different SGA/PGA per instance, just as you do with the caches for SQL Server across different instances. However, Oracle uses shared code for the daemons (or Services in Windows parlance), so the overhead for the shared code isn't as big.
If you're creating Oracle instances on Windows, you can share one Oracle listener across all of the instances, so you just end up with a couple of services per instance.
Yes, there is overhead. But it's not as large an overhead as it used to be (thinking back to earlier versions of Oracle.)
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