PoolName is the jndi name the DataSource is bound under. Therefore the simplest solution is to change PoolName to DefaultDS.
If you don't do that, you need to tell your app to use OracleDB as the jndi name of the DataSource. Reading the manual is the best way to find out how to do this: I think you change a datasource entry in standardjaws.xml and provide a resource-ref entry in your jboss.xml or ejb-jar.xml.
In any case you will want to also change the type mapping properties in standardjaws.xml to Oracle, and if necessary in jaws.xml.
Thanks very much for the help.
It was not mentioned anywhere in Jboss2.2 doc that we need to change anything other than jboss.jcml. Second, surprisingly I had the same configuration running a while back with same jboss version. I had to format my PC and thats why I had to re-download everything. I swear I never touched jaws/standardjaws/jboss/ejb-jar to point to Oracle before. This fact made things confusing for me. Anyway, I think I can have it working now.
A rather easy thing; but Im not able to find a quick reference. How do I access Hypersonic (DefaultDS) ? I mean how can I run "sqlplus" counterpart of Oracle?