You can create external tables when you need to access data in a remote table. The external table has all the properties of the remote table but it does not contain any data locally.
External tables are metamodel extensions defined in the profile category of an extended model definition attached to a PDM. For example, in Sybase ASA, external tables are called proxy tables and a specific extended model definition is delivered to let you design these tables.
For more information on designing proxy tables in Adaptive Server® Anywhere and Adaptive Server® Enterprise, see Working with Proxy Tables in Sybase ASA and ASE.