Appendix C: WebLogic Clustering for High Availability
About WebLogic Clustering
WebLogic Server clusters provide scalability and reliability for your applications by distributing the workload among multiple instances of WebLogic Server. Incoming requests can be routed to a WebLogic Server instance in the cluster based on the volume of work being processed. In case of hardware or other failures, session state is available to other cluster nodes that can resume the work of the failed node.
A WebLogic server cluster consists of multiple WebLogic server instances running simultaneously to provide increased scalability and reliability. A cluster appears to clients to be a single WebLogic server instance. The server instances that constitute a cluster can run on the same machine, or be located on different machines. You can increase a cluster's capacity by adding additional server instances to the cluster on an existing machine, or you can add machines to the cluster to host the incremental server instances.
Note: Each server instance in a cluster must run the same version of WebLogic.
Relationship between Clusters and Domains
A domain is an interrelated set of WebLogic server resources that are managed as a unit. A domain includes one or more WebLogic server instances, which can be clustered, non-clustered, or a combination of clustered and non-clustered instances. A domain can include multiple clusters. A domain also contains the application components deployed in the domain, and the resources and services required by those application components and the server instances in the domain. Examples of the resources and services used by applications and server instances include machine definitions, optional network channels, connectors, and startup classes.
In each domain, one WebLogic server instance acts as the Administration Server—the server instance that configures, manages, and monitors all other server instances and resources in the domain. Each domain contains one Administration Server only. If a domain contains multiple clusters, each cluster in the domain has the same Administration Server. All server instances in a cluster must reside in the same domain; you cannot split a cluster over multiple domains. Similarly, you cannot share a configured resource or subsystem between domains.
Clustered WebLogic server instances behave similarly to non-clustered instances, except that they provide failover and load balancing. The process and tools used to configure clustered WebLogic server instances are the same as those used to configure non-clustered instances. However, to achieve the load balancing and failover benefits that clustering enables, you must adhere to certain guidelines for cluster configuration.
High Availability with WebLogic Clustering
Unifier can utilize WebLogic clustering to continue processing data when a server instance fails. You cluster Unifier by deploying it on multiple server instances in the cluster. If a server instance on which Unifier is running fails, then another running server instance on which Unifier is deployed can continue to process data.
For a more comprehensive product overview, documentation, and community forums for WebLogic and its clustering functionality, refer to: http://www.oracle.com/technetwork/middleware/weblogic/overview/index.html
Introduction to High Availability
High availability allows application processing to continue when a server instance fails and provides a reliable environment with minimal or no loss of service. High Availability is often achieved through the use of clusters, units of servers running concurrently to provide application failover and load balancing. Enterprise application deployments can benefit from the additional reliance and flexibility high availability systems provide.
Reasons for Implementing High Availability
Mission critical computer systems need to be available 24 hours a day, 7 days a week, and 365 days a year. However, part or all of the system may be inoperable during planned or unplanned downtime. A system's availability is measured by the amount of time that it provides service over the total time elapsed since the system's initial deployment.
System downtime may be categorized as planned or unplanned. Planned downtime refers to scheduled operations that render the system unavailable. The effect of planned downtime on end users is typically minimized by scheduling downtime when system traffic is slow. Unplanned downtime is any sort of unexpected failure. Unplanned downtime may have a greater effect than planned downtime because it can happen at peak hours, disrupt business operations, or lead to lost productivity or revenue.
When designing your Unifier implementation, it is important to recognize the cost of downtime to understand how your services can benefit from availability improvements.
High Availability Options for Unifier
WebLogic Clustering enables you to provide high availability for Unifier applications, ensuring your services remain scalable and resilient against unexpected failures.
Prerequisites for WebLogic Clustering
This guide assumes that you have already installed and configured Unifier.
Note: The installation wizard deploys Unifier to a single managed server assigned to a cluster within a WebLogic domain. For information on WebLogic Domains, see Creating a WebLogic Domain in the Fusion Middleware documentation at https://docs.oracle.com/en/middleware/fusion-middleware/14.1.2/wldcw/preface.html.
In addition to the prerequisites to enable WebLogic clustering on your initial Unifier deployment, which are described in either Installation Prerequisites of the Installation and Configuration Guide or Prerequisites in Manual Deployment Guide, you will need to install a supported version of Oracle HTTP Server. For a supported version of Oracle HTTP Server, refer to the Unifier Tested Configurations document.
Deploying Unifier with WebLogic clustering requires you to install WebLogic on each machine that will use the Unifier domain, which was created by the Unifier configuration wizard.
Note: You must install the same version of WebLogic on each machine.
Setting Up WebLogic Clustering for Unifier Applications
After you have installed and configured Unifier, you can add new machines, servers, and clusters using the WebLogic Administration Console. You must then add any new servers to different machines and create a cluster to utilize high availability for your application deployments. After creating a cluster, you must add servers to the cluster. For detailed instructions, see Next Steps After Configuring the WebLogic Server Domain in the Oracle WebLogic Server documentation at https://docs.oracle.com/en/middleware/fusion-middleware/weblogic-server/14.1.2/wlsig/next-steps-after-configuring-weblogic-server-domain.html.
Last Published Wednesday, August 5, 2026