Parameter and Command Reference > Logging Configuration Parameters > LogMaxSizeKBs 

LogMaxSizeKBs 
Maximum log file size (in KB). If you do not want to restrict the log file size, type -1. The LogExpireAction parameter determines how a log file is handled after it has reached its maximum size.
This parameter is used for standard logging streams.
 
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.