The blog provides the detailing on how Web Logic Clustered environment is different from Non-clustered environment. Before that , please find below the blog link on the Web Logic Server Clustering Overview
The Clustered Environment is similar to Non-Clustered Environment except from the point that Cluster Web Logic Clustered Environment will provide below given additional features which are quire useful in case of time critical applications which are not supported through non-clustered environment.
Fail over :
Failure is the process when the web logic server is executing an object which could be the web logic resource, application component / service which needs to be completed as per the received service request but fails due to some reason.
In the Non-clustered environment, this failed object cannot be recovered or cannot instantiate a new object copying the failed object details to resume its processing. The clustered environment provides that support.
The clustered environment maintains the copy of the failed object.
The Web Logic program which manages failover process should be having the Object information which are in process including the location, operational status and overall progress of the in process object.
Web Logic Server also maintains the information regarding the IP Sockets and Java Naming and Directory Interface (JNDI) to share and maintain information about each object running in the Web Logic clustered environment.
Web Logic Server maintains the State of an object (what has been done for the object) using the Session Replication and Replica Aware Stubs techniques.
To avoid huge load on a single server, the Web Logic Clustered environment uses the technique of Load Balancing to ensure fair load on each server instance to increase performance, scalability and reliability of executed services.
Load balancing is the mechanism through which distribution of jobs will be performed using the Load Balancing Algorithm. By default, Web Logic uses Round-Robin Algorithm.
Automatic Migration Process:
Also Web Logic Clustering provides the Automatic Migration Process which means migration of clustered server instances from one machine to another at the run time to avoid failure of the in progress services / applications.