If I had a local-tx-datasource defined, I can set connection properties like this:

<local-tx-datasource>
 ...
 <!-- You can include connection properties that will get passed in
 the DriverManager.getConnection(props) call;
 look at your Driver docs to see what these might be. -->
 <connection-property name="char.encoding">UTF-8</connection-property>
 <!-- Tells an Oracle 10g driver to properly implement clobs. -->
 <connection-property name="SetBigStringTryClob">true</connection-property>
 ...

But, if I were to convert this to an xa-datasource, I see no way of telling it to set those connection properties. "BigStringTryClob" is not an attribute on Oracle's XADataSource so I can't use:

<xa-datasource-property name="BigStringTryClob">true</xa-datasource-property>

How can I set connection properties on XA data sources? And specifically, how to I set that big-string-try-clob configuration?