diffrence between local-tx-datasource xa-datasource

[zhangj]

I'm reading the Jboss document,I'm no quite understand the diffrence of local-tx-datasource and xa-datasource,I'm not sure when should use which

[adrian.brock]

XA if your db supports it and you are doing work with more than one transactional
resource.

If you are only doing jdbc (i.e. no jms or other transactional resource) you only need local.

Search the internet for XA, two phase commit, etc.
or read the J2ee Connector spec.