Internal Exception: java.sql.SQLException: javax.resource.ResourceException: IJ000453: Unable to get managed connection for java:jboss/datasources/TestDS
1) Check for the database, whether its up or not.
2) Check for the datasource configuration from JBoss console(usually http://localhost:9990/console). Make sure the connection parameters are correct.
3) Check for the network connection between the database server and the Jboss server is ok.
4) If the databse is PostgreSql, then make sure that the database is not limited for opening number of concurrent connection.