I need to set this on a lab instance to install CDH. This is taken from the install guide for CDH.
JNDI name syntax
If you want to use JDBC connection pooling to connect to your external database, specify the JNDI name. The required syntax for the JNDI name is java:comp/env/jdbc/<Data Source>. Replace <Data Source> with the name of the resource set in the config.xml file on the application server.
See below for an example of the syntax. The data source in the example is set to mktDataSource.