LGWR (ospid: Xxx): Terminating The Instance Due To Error 4021

刘泽宇

备库由于不明原因宕掉了，查看alert日志中，有这样的记录：Erros in file /u01/.../test_lgwr_27083.trc:
ORA-04021: timeout occurred while waiting to lock object
LGWR (ospid: 14558): terminating the instance due to error 4021
opiodr aborting process unknown ospid (27083) as a result of ORA-1092
System State dumpe requested by (instance=1,osid=27083(LGWR)),summary=[abnormal instance termination].
System State dumped to trace file /u01/.../test_diag_27067_20210324144428.trc
Instance terminated by LGWR, pid = 27083

根据官方文档(ID 2177473.1)
这是一个在11.2.0.4中已经得以解决的bug，不过默认是disabled
要启用修复的方法，将"_adg_parselock_timeout"这个参数设置为LGWR在退出并重试请求前应等待的厘秒数（number of centi-seconds）
如：
ALTER SYSTEM set "_adg_parselock_timeout"=550 scope=both;

这样能够阻止备库由于LGWR解析锁而崩溃，但是建议对主库进行检查，找到导致LGWR解析锁的根本原因