In an intranet production environment we have running a Glassfish v2 appserver with several J2EE applications which all use JexcelApi , a.k.a JXL, which is an open source library for accessing, generating or manipulating Microsoft Excel documents. We use version 2.6.3 of JXL because it's the recent one in the Maven repository which we use, however, at the official JXL site there are newer versions. Additionally we have log4j and Java Commons Logging (JCL), ignoring Glassfish's JSR-47 Java Util Logging (JUL) facility. Application #1 uses purely log4j and gets its log4j.xml config from a custom location. Application #2 runs Java Commons Logging with no explicite configuration file given, so JCL uses the default JUL facility of the appserver. Application #1 had been running for a long time without problems but when we installed #2 we realized that a jxl.log file had been created in the glassfish/domain/domain1/config directory and it's rapidly growing. As it happens, we