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Introducing PAS for OpenEdge
Comparing PAS for OpenEdge to the OpenEdge AppServer : Comparing the architecture of the OpenEdge AppServer and PAS for OpenEdge

Comparing the architecture of the OpenEdge AppServer and PAS for OpenEdge

The Progress Application Server for OpenEdge is an Apache Tomcat Web server and servlet container that is customized to provide application server support for OpenEdge applications and to respond to HTTP/HTTPS client requests.
If you are accustomed to working with the OpenEdge AppServer, you will find that PAS for OpenEdge is different. For example:
*The OpenEdge AppServer must be configured with an external Web server with adapters (AIA, REST, SOAP) in order to respond to HTTP/HTTPS client requests.
PAS for OpenEdge responds directly to HTTP/HTTPS requests because it is a Web server with a default ROOT application configured to support APSV (analogous to AIA), REST, and SOAP requests.
*Client requests handled by PAS for OpenEdge are not managed and routed by a NameServer process.
*A single PAS for OpenEdge instance supports both session-managed and session-free connection models. With OpenEdge AppServer, you must run a separate instance for each session model and operational mode that you need to support.
The following figure illustrates the difference in the overall architectures of the two servers.
Figure 3. OpenEdge AppServer compared to PAS for OpenEdge
Architectures of Classic AppServer and PASOE
Notice that the OpenEdge AppSever must be configured with a separate Web server in order to support HTTP/HTTPS clients. In addition, the Web server must be configured with appropriate adapters in order to communicate with the OpenEdge AppServer.
Also notice that multiple AppServer instances are required to support each operational mode, in this case state-aware and state-free. An optional NameServer directs the client request to the server running in an appropriate operational mode.
By comparison, PAS for OpenEdge is a simpler, more direct, and more efficient architecture. There is no need to install and configure a separate Web server with adapters. PAS for OpenEdge is the Web server. Moreover, a single PAS for OpenEdge instance can run sessions in both operational modes.