In many application servers you can't map CMP's to multiple tables. It's just not possible. In those application servers that allow it, it is unique to each application server. If you will tell us which application server (and version) you are using, we could possibly give you some advice as to if, or how it can be done.
In any case, the spec is totally silent on the issue of mapping to database tables, so it won't be in the deployment descriptor anyway -- usually it's in some "extra" file or descriptor unique to the vendor.
Kyle
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Kyle Brown,
Author of
Enterprise Java (tm) Programming with IBM Websphere
See my homepage at
http://members.aol.com/kgb1001001 for other WebSphere information.