How to control logging to the em.log file

Document ID : KB000029515
Last Modified Date : 17/04/2018
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Question:
When using the EM_HOME/bin/EMCtrl.sh script to start the Enterprise Manager a file em.log is created in directory EM_HOME/logs which contains the same information as the IntroscopeEnterpriseManager.log files. However unlike the IntroscopeEnterpriseManager.log files which wrap after 200MB & have a limited backup number(default of 4), the size of the em.log keeps increasing. How can the em.log logging be turned off?
Environment:
Introscope Enterprise Manager running on Linux/Unix
Answer:
The logging to the em.log represents the log4j console output and duplicates the log4j logfile output to the file IntroscopeEnterpriseManager.log.
To disable logging to the em.log, the console option should be removed from property "log4j.logger.Manager" in IntroscopeEnterpriseManager.properties i.e.
CHANGE: log4j.logger.Manager=INFO, console, logfile
TO: log4j.logger.Manager=INFO, logfile

NOTE: At start up a small em.log file will still be created from the initial standard out/console redirection but once the Enterprise Manager is fully up and the log4j setting has been processed the em.log logging will then stop. 
To completely disable em.log creation from startup a modification can be made to the EM_HOME/bin/EMCtrl.sh script as follows:
CHANGE: nohup "$EMCmd" >> "$LOGFILE" 2>&1 & 
TO: nohup "$EMCmd" > /dev/null 2>&1 & 
Additional Information:
There is no log4j property to limit the actual size of the em.log file.