Let's say something like this is showing in the log.

dd-mm-yyyy hh:mm:ss.sss INFO [Timer-0] org.apache.catalina.loader.WebappClassLoaderBase.checkStateForResourceLoading Illegal access: this web application instance has been stopped already. Could not load [DB2JccConfiguration.properties]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.
java.lang.IllegalStateException: Illegal access: this web application instance has been stopped already. Could not load [DB2JccConfiguration.properties]. The following stack trace is thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access.

This suggests there is some issue with the DB2 database driver JAR being used. Check out my article on installing the JDBC connector in Tomcat.