Java OJDBC Oracle SQL查询每隔几个月挂起一次

We have a multi-threaded java application with a Web UI and REST API that is compiled using java 6 and runs in tomcat 6. During operations it uses OJDBC to access its Oracle DB millions of times a day. Once every two or three months one of the DB queries hangs and never returns, which causes part of the application to stop processing and a backlog to get created. Other threads are able to communicate with the DB and do their work, only one thread gets hung, which unfortunately stops file processing.We have a multi-threaded java application with