undo系列学习之如何计算最优的undo_retention及undo_retention的初体验(二)
MByte]",
SUBSTR(e.value,1,25) "UNDO RETENTION [Sec]",
ROUND((d.undo_size / (to_number(f.value) *
g.undo_block_per_sec)))"OPTIMAL UNDO RETENTION [Sec]"
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, www.2cto.com
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'
ACTUAL UNDO SIZE [MByte] UNDO RETENTION [Sec] OPTIMAL UNDO RETENTION [Sec]
30 900 40421
作者 linwaterbin