If you are using log4j you can also get it to print out memory usage which can be helpful:
# ***** P is set to be a RollingFileAppender.
log4j.appender.P=org.apache.log4j.RollingFileAppender
log4j.appender.P.Threshold=WARN
log4j.appender.P.File=/Logs/Pattern/log.txt
# ***** Max file size is set to 100KB
log4j.appender.P.MaxFileSize=1000KB
# ***** Keep one backup file
log4j.appender.P.MaxBackupIndex=100
# ***** R uses PatternLayout.
log4j.appender.P.layout=er.extensions.ERXPatternLayout
log4j.appender.P.layout.ConversionPattern=%W{n[]} %V{u used/f free} %-5p %d{dd/MMM/yyyy HH:mm:ss} (%c{1}:%L) %X{logID} %m%n