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Application Migration and Development Guide
Application Development with PAS for OpenEdge : PAS for OpenEdge and Client Interaction : Understanding synchronous and asynchronous requests : Specifying the type of remote request
Specifying the type of remote request
The type of remote request (synchronous or asynchronous) is determined by options on the RUN statement. A PAS for OpenEdge instance can handle both types of requests running in either a session-managed or session-free application model.
You can initiate as many asynchronous requests as you want at any point during client execution. You can also mix synchronous and asynchronous requests in the same application. The one constraint is that you can initiate a synchronous request only if there are no pending (incomplete) asynchronous requests over the same connection to a PAS for OpenEdge instance. OpenEdge also provides a mechanism for you to check the status of asynchronous requests for a session-managed or session-free connection.
Note: As suggested earlier, the ABL session agent that executes a request does not know if the request is synchronous or asynchronous. The session manager manages each request on behalf of the client, and dispatches the request for execution according to the application model. Consequently, the client can execute synchronous and asynchronous requests without regard to the application model.