Community

Here is an use-case:

<datasources>
  <xa-datasource>
    <jndi-name>PostgresDS</jndi-name>
    <track-connection-by-tx>true</track-connection-by-tx> 
    <xa-datasource-class>org.postgresql.xa.PGXADataSource</xa-datasource-class>
    <xa-datasource-property name="ServerName">server_name</xa-datasource-property>
    <xa-datasource-property name="PortNumber">5432</xa-datasource-property>
    <xa-datasource-property name="DatabaseName">database_name</xa-datasource-property>
    <xa-datasource-property name="User">user</xa-datasource-property>
    <xa-datasource-property name="Password">password</xa-datasource-property>

    <metadata>
       <type-mapping>PostgreSQL 8.0</type-mapping>
    </metadata>

  </xa-datasource>
</datasources>

There isn't a security-domain defined here.