ORACLE RAC ADG备库报错ORA-04021: timeout occurred while waiting to lock object

问题：核心的灾备 RAC ADG 备库，这两天频繁重启，并且报如下错误，通过查看MOS，发现是个BUG

ADG备库的ALERT错误日志如下：

Errors in file /u01/app/oracle/diag/rdbms/hxxxsz/hxxxsz1/trace/hxxxsz1_lgwr_69711.trc:

ORA-04021: timeout occurred while waiting to lock object

Mon Dec 16 16:26:15 2024

ORA-01555 caused by SQL statement below (SQL ID: 87gaftwrm2h68, Query Duration=899 sec, SCN: 0x05cf.7a01a7dc):

select o.owner#,o.name,o.namespace,o.remoteowner,o.linkname,o.subname from obj$ o where o.obj#=:1

LGWR (ospid: 69711): terminating the instance due to error 4021

Mon Dec 16 16:26:15 2024

System state dump requested by (instance=1, osid=69711 (LGWR)), summary=[abnormal instance termination].

System State dumped to trace file /u01/app/oracle/diag/rdbms/hxxxsz/hxxxsz1/trace/hxxxsz1_diag_69557_20241216162615.trc

Mon Dec 16 16:26:15 2024

ORA-1092 : opitsk aborting process

Mon Dec 16 16:26:16 2024

License high water mark = 1321

Instance terminated by LGWR, pid = 69711

USER (ospid: 42412): terminating the instance

Instance terminated by USER, pid = 42412

Mon Dec 16 16:26:23 2024

Starting ORACLE instance (normal)

************************ Large Pages Information *******************

Per process system memlock (soft) limit = UNLIMITED

解决方案:

查看隐藏参数：

SELECT ksppinm, ksppstvl, ksppdesc FROM x $ksppi x, x$ ksppcv y WHERE x.indx = y.indx AND ksppinm ='_adg_parselock_timeout';

KSPPINM

KSPPSTVL

KSPPDESC

_adg_parselock_timeout

timeout for parselock get on ADG in centiseconds

执行以下语句：

alter system set "_adg_parselock_timeout"=500 scope=both sid='*';

参考MOS内容如下：

ORA-04021: timeout occurred while waiting to lock object : DR Instance terminated by LGWR (Doc ID 2183882.1)

Applies to:

Symptoms

Cause

Solution

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| Issue matches with bug 11712267 and bug 16717701 Since two bugs are matching with the case, You can try with option (1) . As per Bug 11712267 change the cursor_sharing to force on Active dataguard (ADG). Monitor your environment for sometime. If it crashes again then follow with the option (2) Option (2): As per bug description LGWR can request DBINSTANCE lock in X mode without any timeout which can lead to a hang / deadlock. Both fixes are already included in 11.2.0.4 but the fix is DISABLED by default. == > To ENABLE the fix one has to set == > "_adg_parselock_timeout" > to the number of centi-seconds == > LGWR should wait before backing off and retrying the request. Value should be in centi seconds. == > I Don't think there is really any hard fast rule for a value - at default (0) it will not timeout. A value representing a few seconds seems reasonable - if LGWR has been stuck for say 5 seconds waiting it seems reasonable guess it is not going to get the lock. The param just causes it to abort the current attempt and retry If you want to play safe can start with a higher value then decrease later. A higher value will just mean more sessions blocked for longer in case of the deadlock situation. 500 Seems reasonable , but I have no data to base it on. There should be a statistic "ADG parselock X get attempts" If it gets set too small that value would likely increase a lot due to keep timing out and retrying. This is a dynamic parameter Follow option (1) . change the cursor_sharing to force on ADG If issue re-appears then follow option (2) as below Please set "_adg_parselock_timeout" to 500 == > SQL > alter system set "_adg_parselock_timeout"=500 scope=both sid='*'; |