Oracle's XA driver has limitations when trying to resuse
connections that have been already used either inside or
outside a transaction.
To workaround this problem, you can now specify
<no-tx-separate-pools/> in the oracle-xa-ds.xml
This provides two separate pools.
Which pool is used depends upon whether a transaction is
active when you ask for a connection from the data source.
For ByApplication and ByContainerAndApplication
pooling, the number of available pools are doubled.