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Quoting from Oracle documentation about logical storage structures:

A database must have the SYSTEM and SYSAUX tablespaces:

alt text

Why is it compulsory to have these tablespaces?

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up vote 10 down vote accepted

Tradition and the ability for elegant failure degradation.

As the database has evolved over 11 versions, important views and tables that maintain and support the database have been programmed into the two tablespaces. Furthermore, they represent a fantastic logical separation between the "NEVER EVER TOUCH" and the "third parties can put stuff here."

From the docs:



Thus, while it's critical to have the SYSTEM tablespace never ever fail, one doesn't need to be nearly as paranoid for SYSAUX, this allows the designers to keep the size of SYSTEM down, while allowing third-party auxiliary features to be part of the "core" database.

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So the same reason why Microsoft includes so much stuff in Windows. :p ... This is also why some people complain about the cruft of Oracle, and you can't get away from those complaints on any system, more or less. –  jcolebrand Jan 11 '11 at 16:18
That, and it's handy to have a "miscellaneous" area that has all your third-party stuff that... if it has an accident... won't nuke anything else. –  Brian Ballsun-Stanton Jan 12 '11 at 0:38

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