Replicating data

To enable the sharing of data among processes and the backing up of failed processes, you can use the replication service provided by WebSphere Application Server. To use the service, you define replication domains, which list interconnected replicator entries (residing in managed servers in the cell) that can exchange data.

There are two ways to define replication domains and replicator entries:

  • One can use the Internal Replication Domains page and Replicator Entry page to define replication domains and replicator entries. To access the Internal Replication Domains page, click Environment > Internal Replication Domains in the console navigation tree. To access the Replicator Entry page, click a replication domain on the Internal Replication Domains page and then click Replicator Entries. When you create the entries on the Replicator Entry page, you can select any server for the replicator to reside in. The page lists all servers in the cell that do not already have replicators defined.

  • One can define replication domains and replicator entries when you create a cluster on the Create New Cluster page. Using the page allows you to create a replication domain that has the same name as the cluster and, as you add or create new appservers in the cluster, define replicator entries in those servers. To access the Create New Cluster page, click Servers > Clusters in the console navigation tree to go to the Server Clusters page and click New.

A replicator does not need to run in the same process as the application server that uses it. However, it might be easier to manage replicators and replication domains if a one-to-one correspondence exists between replicators and appservers. During configuration, an application server connects by default to its local replicator, so you do not need to explicitly specify the replicator to use. All processes share equally in the replication cost.

 

  1. Create an application server. Later, enable a replication domain and its replicators (step 2).

    Or, create a cluster and add an application server to it. When you define the cluster, you can specify that you want a replication domain associated with the cluster. Also, when you define a cluster, you can specify that you want a replicator associated with an appserver. For example, you might specify that a replicator launch in the same Java Virtual Machine as a Web container. Or, you can enable a replicator later (step 2).

  2. Create a replication domain if one is not already created for the processes you want supported by data replication. Go to the Replication Domains page and click New. On the settings for a replication domain instance, specify values for the instance. The default values generally will be sufficient, especially as to pooling and timeout values.

    1. Name the replication domain.

    2. Specify the timeout interval.

    3. Specify the encryption type. The DES and TRIPLE_DES options encrypt data sent between WebSphere Application Server processes and better secure the network joining the processes.

    4. Partition the replication domain to filter the number of processes to which data is sent. Partitioning the replication domain is most often done if you are replicating data to support retrieval of an HttpSession if the process maintaining the HttpSession fails. Partitioning is not supported for sharing of cached data maintained by Web container dynamic caching.

    5. Specify whether you want a single replication of data to be made. Enable the option if you are replicating data to support retrieval of an HttpSession if the process maintaining the HttpSession fails.

    6. Specify whether processes should receive data in objects or bytes. Processes receiving data in objects receive the data and class definitions. Processes receiving data in bytes receive the data only.

    7. (Optional)  

      Configure a pool of replication resources. Pooling replication resources can enhance the performance of the internal data replication service.

  3. Create replicators for the processes you want supported by data replication, if replicators have not already been created for the processes. The default convention is to define a replicator in each appserver that uses replication. However, you can define a pool of replicators, separate from the servers hosting applications.

    1. Click on the replication domain instance on the Replication Domains page and then Replicator Entries to access the Replicator Entry page.

    2. Click New and, on the replicator entry settings page, define a replicator. Specify a replicator name and, from the drop-down list of the available servers within the cell to which you can assign a replicator, select a server. Also specify a host name and ports. Note that a replicator has two end points (replicator and client end points) that use the same host name but have different ports.

  4. If you use the DES or TRIPLE_DES encryption type for a replicator, click RegenerateKey on the settings for a replication domain instance at regular intervals, such as monthly.

    Periodically changing the key enhances security.

Replication
Configure cache replication
Internal messaging configuration settings
Internal replication domain collection

 

WebSphere is a trademark of the IBM Corporation in the United States, other countries, or both.

 

IBM is a trademark of the IBM Corporation in the United States, other countries, or both.