SQL> create rollback segment rbs06 tablespace rbs storage (initial 8388608 next 8388608 maxextents unlimited optimal 209715200); create rollback segment rbs06 tablespace rbs storage (initial 8388608 next 8388608 maxextents unlimited optimal 209715200) * ERROR at line 1: ORA-01593: rollback segment optimal size (25600 blks) is smaller than the computed initial size (40960 blks) SQL> create rollback segment rbs06 tablespace rbs storage (initial 8388608 next 8388608 maxextents unlimited); Rollback segment created. SQL> alter rollback segment rbs06 storage (optimal 209715200); Rollback segment altered.