Here are some tips to setup a datasource in JBoss: JBOSS 3.0.4 Oracle 8.1.7 (I am taking Oracle as an example) Platform is WinNT
1. Put Oracle JDBC driver zip file classes12.zip in $JBOSS_HOME/server/default/lib. If you are using some other RDBMS, use the appropriate JDBC driver file for this purpose.
2. Modified oracle-service.xml from $JBOSS/docs/examples/jca There are separate templates available in this directory for different RDBMS/datasources. Modify the template and put appropriate information. Things that can be changed may differ. Here are a few for RDBMSes: a. URL b. UserName c. Password
3. Copied oracle-service.xml to $JBOSS_HOME/server/default/deploy Copy the modified file to the directory.
I had to spending lot of time finding information and sorting things out before things started working. Hope this posting helps save some of your precious time.
For more insight into Oracle XA configuration, see my posting on the same.