12c Alert Log Appears To Show Unexpected Instance Restart (Doc ID 2049516.1)

Symptom

The human readable text mode alert log appears to show startup messages, with no preceding shutdown messages or any other messages indicating any kind of error condition.  

It then shows the standard startup information like banner, system parameters with non-default values, and a dump of current patch information, for example:

Chis is new behaviour in 12c, and does not reproduce in 11.2.0.4 or older versions.  What happened here was that the XML alert log log.xml file reached 10MB in size.  At that time it is segmented and a new log_<n>.xml file is created. Every time that log.xml is segmented, information about all startup parameters and patch information is dumped to the alert.log.

This does not indicate any kind of error condition in the DB and normal activity continues throughout this time.

If this really would be an unexpected DB restart, then the timestamps before and after show a sub-second restart time.

The behaviour only could become a problem if the system is generating lots of log messages for some reason.
For example, Enhancement Request
Bug 21326339 - "CURRENT PROCESS FOR SEGMENTING LOG.XML CAUSES PROBLEMS"
addresses a situation where LogMiner is being used with supplemental logging, which generates a lot of information so the log.xml reaches 10Mb very soon (sometimes every 9 minutes).
As a result the alert log contains plenty of duplicate information and grows too quickly.

Note that above enhancement request has been rejected because underscore parameters are already available to control the information being dumped in the alert log when that log file is segmented.
 

SOLUTION

No actual action is required as this alert log text file content is expected behavior based on segmented log.xml files. There is nothing wrong with the database. It did not crash and restart.

However, if you absolutely want to prevent the extra information logging, you can do so be setting below parameters:

• To avoid dumping the parameters information upon log.xml segmentation:
  _log_segment_dump_parameter=FALSE
    
  
• To avoid dumping the patch information upon log.xml segmentation:
  
  _log_segment_dump_patch=FALSE