Bruce W Cassidy (8/13/2009)
Oracle uses shared code for the daemons (or Services in Windows parlance), so the overhead for the shared code isn't as big.
Sorry, on this one you are dead wrong man 😀
Providing all your instances point to the same ORACLE_HOME it's true that you are going to end up with a single set of binaries BUT -notice the uppercase but? - Oracle starts one PMON per instance, one SMON per instance, etc, etc, etc. therefore you end with as many as 30 daemons per instance.
Bruce W Cassidy (8/13/2009)
If you're creating Oracle instances on Windows, you can share one Oracle listener across all of the instances
You CAN... but you don't want to do it so pretty please allow at least one listener per instance.
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Pablo (Paul) Berzukov
Author of Understanding Database Administration available at Amazon and other bookstores.
Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.