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Introducing PAS for OpenEdge
Comparing PAS for OpenEdge to the OpenEdge AppServer : ABL Sessions

ABL Sessions

Note the following differences between the OpenEdge AppServer and the Progress Application Server (PAS) for OpenEdge with regard to ABL sessions:
*In the OpenEdge AppServer, each agent is an OS process that handles a single ABL session.
In PAS for OpenEdge, an agent is a single OS process that can run multiple ABL sessions. It is often referred to as a Multi-session Agent (MSAgent).
*The ABL Session Manager in PAS for OpenEdge is not identical to, but is functionally similar to the broker in the OpenEdge AppServer. It responds to client requests by communicating with an agent process to assign a session, to make sure that ABL code executes, and to ensure that a response is returned to the client. If there are no free sessions in one agent, it launches another agent.
Note: You configure properties (the number of sessions supported by an agent, the number of agent processes allowed in a server, etc.) in a PAS for OpenEdge instance's /conf/ file. It is similar in format to the file, but it only applies to a single instance. All individual PAS for OpenEdge instances have their own file.
*Unlike the OpenEdge AppServer, you do not need to run a separate instance of PAS for OpenEdge in a mode to support a particular session model. In other words, a single instance of PAS for OpenEdge supports both session-managed and session-free connections.
The client request determines the mode of the session. Sessions running in different modes can run concurrently on a single instance of PAS for OpenEdge.
*In PAS for OpenEdge, you must specify separate startup/shutdown procedures for agents and sessions. In the Classic OpenEdge AppServer, the srvrStartupProc and srvrShutdownProc procedures execute on both agent and session start/stop events because the Classic AppServer agent is bound to a single session.
In PAS for OpenEdge, you specify startup/shutdown procedures in an instance's /conf/ file. You modify the sessionStartupProc and sessionShutdownProc properties to specify the procedures that execute on ABL session start/stop events. You modify the agentStartupProc and agentShutdownProc properties to specify the procedures that execute on agent start/stop events.