With this setting, v$undostat.tuned_undoretention is not calculated based on a percentage of the fixed size undo tablespace, instead v$undostat.tuned_undoretention is set to the maximum of (maxquerylen secs + 300) undo_retention specified in init.ora file.
3.) Set the following hidden parameter in init.ora:
_undo_autotune = false
or
SQL> Alter system set "_undo_autotune" = false; 可动态调整无需重启数据库。
Autotune of undo retention is turned off.
Wed Jan 30 20:59:26 GMT+08:00 2013ALTER SYSTEM SET _undo_autotune=FALSE SCOPE=BOTH;
SQL> show parameter undo
NAME TYPE VALUE
------------------- ----------------- ----------
_undo_autotune boolean FALSE
undo_management string AUTO
undo_retention integer 900
undo_tablespace string UNDOTBS1
在设定完_undo_autotune后，并且结果应用方跑存储过程，未发现ORA-30036: unable to extend segment by 8 in undo tablespace 'UNDOTBS1'错误（此错误并没有在alert日志中体现。）