早上数据库出现报错Error ORA-235 Occurred During An Un-locked Control File Transaction，一般碰到ORA错误会先去mos中查找文档，然后在根据文档了解原因及解决方法
Error ORA-235 Occurred During An Un-locked Control File Transaction (Doc ID 2312580.1)
Below error is seen in 18.104.22.168 database alert log:
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.
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.
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