Number of default Rollback segments

[V6163]

We have created a database using DBASSIST wizard with shared mode(MTS enabled), we have done the installation with the default tablespaces. It has created a tablespace RBS and installation went thru. When i checked for this query "SELECT * FROM DBA_ROLLBACK_SEGS" It has listed SYSTEM rollback segment and also other 29 rollback segments
named RBS0 .. RBS29. They are created by default.
Some time before when I created a database it has created only 7 rollback segments. In my installtions no where
i have gave this sought of paramerters.

1) My question is -
on which factor the no. of rollback segments (at the time of
database creation) depends on.
2) I didn't plan for my database for the number of rollback segments. Can i have this many(default) rollback segments initially.

[sambavan]

It might be because of the number of concurrent users you would have specified on the dbassit, which then would have internally callculated the RBS for you. You can always go and reduce the RBS. But remember you will not be able to remove the system RBS. Then also take a look into your init.ora file for the ROLLBACK_SEGMENTS that would tell you how many roll back segments are brought up when you start the instance. More the RBS, would not effect much the database, but make sure that they are all tuned for the operation, that is extent size and optimal number and etc.

Sam