12c 以上报：Error ORA-235 Occurred During An Un-locked Control File Transaction

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Error ORA-235 Occurred During An Un-locked Control File Transaction (Doc ID 2312580.1)       

In this Document
Symptoms
Cause
Solution

APPLIES TO:
Oracle Database - Enterprise Edition - Version 12.1.0.2 and later
Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
SYMPTOMS
Below error is seen in 12.1.0.2 database alert log:

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Tue Sep 26 08:01:33 2017
Error ORA-235 occurred during an un-locked control file transaction. This
error can be ignored. The control file transaction will be retried.
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CAUSE
Expected behavior


SOLUTION
Starting from Oracle 12c, controlfile transactions are enhanced. We are no longer request a controlfile enqueue before scanning a particular controlfile section. This is done to minimize locking issues and improve performance and scalability. Due to this change, the process reading a controlfile section may sometimes encounter ORA-235 if the same section is being modified by another process. When this occurs, the reading process will simply re-read the section again. You can safely ignore this message, it's not an issue.

The errors cannot be suppressed at database level by setting any event or initialization parameter. The reason is that although the errors are harmless, they do give an idea of the concurrency on the controlfile and can help debug issues relating to slow controlfile i/o etc so, this enhancement has been added specifically by development. It's best to modify any monitoring scripts to ignore/exclude this error. Since this is working as designed and these are simply informational, the messages can simply be ignored.