Setting up a high availability environment

Planning ahead for high availability support is important to avoid the risk of a failure without failover coverage. The application server infrastructure that is managed by a high availability manager includes cells and clusters. These components relate closely to core groups, high availability groups, and the policy that controls the high availability infrastructure.

The high availability manager is designed to function in all of the supported WebSphere Application Server topologies. However, a high availability-managed environment must comply to the following rules:

• A cell in a high availability infrastructure is partitioned into one or more core groups. WebSphere Application Server provides a default core group as part of the high availability manager function. Additional core groups can be created using the administrative console.

• A core group cannot extend beyond the boundaries of a cell, and it cannot overlap with any other core groups.

• A cluster must be a member of only one core group. All of the individual members of that cluster must be members of the same core group. This one-to-one relationship between a cluster and a core group exists for both static and dynamic clusters.

• Individual application servers that are part of the high availability environment must also be part of a core group.

• An application server can only join a core group if its JVM can communicate with all of the other online application servers that are part of that core group. If a single application server can not open a connection to the JVM or send a heartbeat to it, the application server is not joined to the core group.

The following diagram illustrates what a cell might look like in a high availability environment:

What to do next

Important: After you set up your WebSphere Application Server environment to comply with all of the high availability-managed environment rules, use the default core group to control this environment. DO NOT add additional core groups unless your environment absolutely requires them. Also, do not change the default configurations unless you are doing so to solve a specific problem or situation. When you do make configuration changes, such as changing the policy for a high availability group or moving core group members between core groups in a multi-core group environment, make sure you fully understand the effect such changes will have on your entire environment. Following are tasks you might perform if you need to change the default configuration:

1. Create additional core groups, if required..

2. Modify the attributes of an existing core group.

3. Modify the attributes of an existing high availability group policy.

4. Create a new policy and associate it with a high availability group.

5. Create core group access points if you create additional core groups.

6. Set up IP addresses for communications within the core group if you are installing the Application Server on a system with multiple NICs.