I am adding an XA declaration to domain.xml:

<xa-datasource jndi-name="java:/H2XADS" pool-name="H2XADS">
<xa-datasource-class>org.h2.jdbcx.JdbcDataSource</xa-datasource-class>
<xa-datasource-property name="URL">jdbc:h2:mem:test</xa-datasource-property>
<security>
<!-- Have to defined as a primary property - otherwise it won't work -->
<user-name>sa</user-name>
<!-- Have to defined as a primary property - otherwise it won't work -->
<password>sa</password>
</security>
</xa-datasource>

After the server has booted it's gone.