The classic AppServer can optionally rely on a NameServer that enables clients to locate AppServer instances by their application service name. Therefore, you do not have to configure the clients with explicit network addresses and ports to access a particular classic AppServer instance. This same NameServer can achieve server fault tolerance and load balancing for a high client load by having access to multiple classic AppServer instances that provide the same application service to clients.

Because it is a web application server, PAS for OpenEdge does not use the OpenEdge NameServer. It does allow the use of a DNS load balancing service and server-side proxies that allow a client to connect to a server resource without having to know the explicit network address and port, thus achieving a similar level of fault tolerance and load balancing using multiple PAS for OpenEdge instances that support the same ABL web application.

All OpenEdge clients must convert to connecting to a URL that identifies both the ABL web application and connection transport supported by the PAS for OpenEdge instances registered with the DNS server. For PAS for OpenEdge REST and SOAP clients, the URL changes similar to the changes required when you move classic AppServer REST or WSA Adapters to a different Web server.

Note: For more information about load balancing configuration options for PAS for OpenEdge, see Load Balance PAS for OpenEdge Instances.