You can do this. It took me a while to work out the correct sequence. What you need to do is define the jdbc/product-ds in your server.xml (tomcat/conf/server.xml) in the GlobalNamingResources section kind of like this:
<GlobalNamingResources>
<Resource name="jdbc/product-ds " auth="Container"
type="javax.sql.DataSource" driverClassName="oracle.jdbc.OracleDriver"
url="jdbc:oracle:thin:@127.0.0.1:1521:mysid"
username="scott" password="tiger" maxActive="20" maxIdle="10"
maxWait="-1"/>
</GlobalNamingResources>
Then you can rename this in your server context.xml (tomcat/conf/context.xml)
Like this:
<ResourceLink
name="jdbc/product-cfg-ds"
global="jdbc/product-ds"
type="javax.sql.DataSource"/>
The global name is then renamed for all applications deployed on the the server. I don't think the global jdbc/product-ds will be available in any application, if you did want it you'd need to add:
<ResourceLink
name="jdbc/product-ds"
global="jdbc/product-ds"
type="javax.sql.DataSource"/>