Parameter and Command Reference > Logging Configuration Parameters > LogExpireAction 

LogExpireAction 
Determines how log files are handled when they exceed the maximum size. Type one of the following to determine how log files are handled when they exceed the MaxLogSizeKBs size:
 
The log file's name is appended with a time stamp, compressed and saved in the log directory. By default, this is a Zip file. Use the LogCompressionMode parameter to specify another compression format.
The log file's name is appended with a number and saved in the log directory. When the next log file reaches its LogMaxSizeKBs size, it is appended with the next consecutive number.
The log file's name is appended with .previous and saved in the log directory. Every time a log file reaches its LogMaxSizeKBs size, it is given the same postfix so it overwrites the old log file.
Only one log file is created per day and is appended with the current time stamp. Log files are archived after they reach the LogMaxSizeKBs size.
NOTE The LogMaxSizeKBs parameter takes precedence over the LogExpireAction parameter. Therefore, if you set LogExpireAction to Day, and the value for LogMaxSizeKBs results in more than one log file, multiple log files is generated per day.
 
Logging and/or LogStream or TaskName
If you set this parameter in the Logging and LogStream sections, the setting in the LogStream section takes precedence for the specified log stream.