Don't understand ORA-01594/5

I'm using Netback to do a full backup of a 9205SE database and I get errors: ORA-01595: error freeing extent (2) of rollback segment (16))

ORA-01594: attempt to wrap into rollback segment (16) extent (2) which is being freed

I am using UNDO tablespace, so I'm confused by the suggestion in the manual: Action: The rollback segment shrinking will be rolled back by the system; increase the optimal size of the rollback segment.

Should I drop the tablespace and create a new one using larger extents?

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Terry Dykstra