When a session-free AppObject is instantiated, a pool of connections to the application service is established, as specified by the run-time properties provided. Once instantiated, methods on that AppObject can be called in accordance with the standard Open Client programming model. In the session-free model, each external method call transparently runs a request using a separate connection from the connection pool. (An external method is one that corresponds to an external ABL procedure on the AppServer.) As such, a multi-threaded application may run remote application service requests concurrently. As each request completes, the connection is released back to the pool and is available for another request.
Connections for persistent procedures are handled slightly differently than for non-persistent procedures. When a persistent procedure is instantiated, a connection is reserved from the connection pool. All subsequent internal procedures and user-defined functions run on that persistent procedure use that same connection. The connection is released back to the connection pool only when the persistent procedure is released by calling the _release() method on the ProcObject.
Unlike persistent procedures, single-run and singleton procedures do not reserve connections. In these cases, the connection is released automatically when the internal procedure or user-defined function is complete. However, the _release() method does clean up client-side resources.
