Configuring cache replication

Use this task to improve performance by configuring the data replication service (DRS) to replicate data from the dynamic cache service across the consumers in a replication domain.

1. In the administrative console, click Servers > Server Types > WebSphere application servers > server_name > Container services > Dynamic cache service.
2. To enable replication, select Enable cache replication.
3. Choose a replication domain.
   Use different replication domains for each type of consumer. For example, dynamic cache should use a different replication domain than session manager. The only replication domains that you can select in this panel include replication domains that are configured to use full-group replication. In a full-group configuration, every cache entry is replicated to every other cache that is configured in the servers that are in the replication domain. If none of the replication domains in your configuration meet these requirements, the list is empty. In this case, create a replication domain or alter an existing replication domain so that you have a replication domain that can perform full-group replication. Refer to the Replicating data across application servers in a cluster topic for more information.
4. Define the dynamic cache replication settings. Click Enable cache replication.
   On this page, you can define when and how often data is replicated across the dynamic cache replication domain. For more information about these settings, refer to the Dynamic cache service settings topic.
5. To enable cache replication on a single server in a non-clustered environment, you must define the following JVM custom properties.
   1. In the administrative console, click Servers > Application Servers > server_name.
   2. Under Server Infrastructure, click Java and process management > Process definition > Java Virtual Machine > Custom properties > New.
   3. Under Server Infrastructure, click Java and process management > Process definition > Servant > Java Virtual Machine > Custom properties > New.
   4. Add the new property name as DynacacheEnableUnmanagedServerReplication and set the value to true.
   5. Add another JVM property to specify the global sharing policy for the base z/OS® server.
      Click New and add a new JVM custom property that is called DynacacheUnmanagedServerReplicationType. Use one of the following values:

      Value	Description
      NOT_SHARED	Cache entries for this object are not shared among different application servers. These entries can contain non-serializable data. For example, a cached servlet can place non-serializable objects into the request attributes, if the class type supports it.
      PUSH	Cache entries for this object are automatically distributed to the dynamic caches in other application servers or cooperating Java™ Virtual Machines (JVMs). Each cache has a copy of the entry at the time it is created. These entries cannot store non-serializable data.
      PULL	Cache entries for this object are shared between application servers on demand. If an application server gets a cache miss for this object, it queries the cooperating application servers to see if they have the object. If no application server has a cached copy of the object, the original application server runs the request and generates the object. These entries cannot store non-serializable data. This mode of sharing is not recommended.
      PUSH_PULL	Cache entries for this object are shared between application servers on demand. When an application server generates a cache entry, it broadcasts the cache ID of the created entry to all cooperating application servers. Each server then knows whether an entry exists for any given cache ID. On a given request for that entry, the application server knows whether to generate the entry or pull it from somewhere else. These entries cannot store non-serializable data.

      If you do not define one of these values, the default is NOT_SHARED.
6. Define sharing policies in the cachespec.xml file.

   This is optional.

   To use cache replication among multiple servants on a base server, you must create a cachespec.xml file to define the cacheable objects that you want to create.

   You can override the global sharing policy by specifying a specific sharing policy in the cache policy. For example, if your global policy is to use Push only, you can change the sharing policy of a specific cache entry by making this change to your cache policy:

   <cache-entry>
   	<sharing-policy>not-shared</sharing-policy>
   	<class>servlet</class>
   	<name>/app</name>
   	<cache-id>
   		<component id="action" type="parameter">
   			<value>portfolio</value>
   			<required>true</required>
   		</component>
   		<component id="JSESSIONID" type="cookie">
   			<required>true</required>
   		</component>
   		<property name="EdgeCacheable">true</property>
   	</cache-id>
   </cache-entry>
   

   For more information about the sharing policies that can be defined in the cachespec.xml file, refer to the cachespec.xml file topic.