Connection Pools reaching their max capacity and over

http://docs.oracle.com/cd/E23943_01/apirefs.1111/e13952/taskhelp/jdbc/jdbc_datasources/ConfigureDiagnosticsForADataSource.html

to make sure you are not leaking connections (forgetting to close them),
in your DataSource configuration go to "configuration"/diagnostics and check the "Profile Connection Leak"
This will generate a "profile-type" element in the jdbc-config.xml and set it to 4.
then in your Connection Pool configuration, click on advanced, and enter some large value for "Inactive Connection Timeout" (should be greater than the JTA timeout IMHO)

For more details, see Oracle Support Doc "How to enable WLS Database Profiling to diagnose database connection problems in Webcenter Content (Doc ID 2071557.1) "