If you are doing auditing (traditional or fine grained auditing), then the internal audit tables aud$ or fga_log$, which are by default in the system tablespace, are getting bigger and bigger over time. So you may want to move them into another tablespace – but that was unsupported in the past. No longer so, as Joel Goodman explains in this recent article:
#1 von Joel Goodman am Mai 15, 2009 - 09:58
Uwe – thanks for pointing DBAs to this.