Oracle: Analyzing UNDO Tablespace

-- UNDO tablespace information

SELECT d.undo_size/(1024*1024) ACTUAL, SUBSTR(e.value,1,25) RETENTION,(TO_NUMBER(e.value) * TO_NUMBER(f.value) * g.undo_block_per_sec) / (1024*1024) NEEDED FROM (SELECT SUM(a.bytes) undo_size FROM v$datafile a, v$tablespace b, dba_tablespaces c WHERE c.contents = 'UNDO' AND c.status = 'ONLINE' AND b.name = c.tablespace_name AND a.ts# = b.ts#) d,v$parameter e, v$parameter f, (SELECT MAX(undoblks/((end_time-begin_time)*3600*24)) undo_block_per_sec FROM v$undostat) g WHERE e.name = 'undo_retention' AND f.name = 'db_block_size';

--UNDO tablespace ever failed?

select to_char(begin_time, 'mm/dd/yyyy HH24:MI:SS'), TUNED_UNDORETENTION, SSOLDERRCNT oraerr_cnt from v$undostat where SSOLDERRCNT !=0;