Create a separate tablespace for rollback segments and, if possible, place the datafiles for this tablespace on a different disk device from other Oracle datafiles.

Never create rollback segments in the SYSTEM tablespace (except for the temporary rollback segment required during database creation; see Chapter 2).

Be sure that there is enough space allocated to your rollback tablespace to allow rollback segments to grow as large as necessary to accommodate large update transactions. Remember that batch transactions tend to be large.

Always use the same value for the INITIAL and NEXT extents for rollback segments (define them in the DEFAULT STORAGE clause of the CREATE TABLESPACE statement). This guideline will prevent space fragmentation by allocating rollback segment space in equal-size chunks.

Remember that each rollback segment must have at least two extents, so the initial size of a segment will actually be the sum of INITIAL + NEXT.

Define an OPTIMAL value so that rollback segments that are required to grow in size to accommodate a large transaction can be shrunk to a more reasonable size. Don’t make this size too small, however, or time will be wasted allocating additional extents to your rollback segments.