WebLogic clustering offers three important benefits:
The capacity of an application deployed on a WebLogic Server cluster can be increased dynamically to meet demand. You can add server instances to a cluster with out interruption of service the application continues to run without impact to clients and end users.
2. Load balancing:
The ability to distribute requests across all members of the cluster, according to the workload on each server.
3. High availability:
A mix of features that ensure applications and services are available even if a server or machine fails. Clients can continue to work with little or no disruption in a highly available environment. WebLogic achieves high availability using a combination of features: replication, failover, and migratable services.