When there is a remote connection to a database from an ABL client, database schema information has to be constructed at the client. This involves network traffic to communicate the schema information from the database server to the client (even local schema caches require updates due to schema changes). For information on local schema caches, see the section on reducing connection times when connecting ABL clients to databases in OpenEdge Deployment: Managing ABL Applications.
By using the server session as the only mechanism to access the database, an ABL client no longer needs to connect to the database. This eliminates network traffic, associated with the delivery of the schema information, to the remote client.