Data replication domains

Data replication domains

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Data replication domains and multi-broker domains both perform the same function, which is to provide data replication between application servers in a cluster. Even though we can still configure existing multi-broker domains with the current version of WAS ND, after you upgrade the deployment manager, we can only create data replication domains in the admin console.
For transitioning users: A replication domain created with a previous version of WAS might be a multi-broker domain. You should migrate these multi-broker domains to data replication domains. Data replication domains enable you to:

Set all of the instances of replication that need to communicate in the same replication domain.
Set the session manager with both types of replication domains to use topologies such as peer-to-peer, and client-to-server to isolate the function of creating and storing replicas on separate appservers.
Control the redundancy of replication for each type of replication domain, because with a data replication domain, we can specify a specific number of replicas.

If we used multi-broker domains with earlier releases of WAS ND, use the following comparison chart to learn the differences between how V5.x and V6.x and V7.0 appservers use the two types of replication domains:

Version 5.x appservers using replication domains V6.x and V7.0 appservers using replication domains
Replication domain types Uses only multi-broker replication domains for replication. Servers that are using the current version of WAS can be configured to use both multi-broker replication domains and data replication domains for replication. The two types of domains provide backward compatibility with multi-broker domains that were created with a V5.x server. You should migrate any multi-broker domains to data replication domains.
Data transport method Uses multi-broker domain objects that contain configuration information for the internal JMS provider, which uses JMS brokers as replicators. Uses data replication domain objects that contain configuration information to configure the high availability framework on WAS ND. The transport is no longer based on the JMS API. Therefore, no replicators and no JMS brokers exist. You do not have to perform the complex task of configuring local, remote, and alternate replicators. The earlier version of WAS did not support data replication domains. The current version of WAS can be configured to perform replication using old multi-broker domains by ignoring any JMS-specific configuration and by using the other parameters to configure replication through the high availability framework.
Replication domain configuration The earlier version of WAS encourages the sharing of replication domains between different consumers, such as session manager and dynamic cache. The current version of WAS encourages creating a separate replication domain for each consumer. For example, create one replication domain for session manager and another replication domain for dynamic cache.
The only situation where you should configure one replication domain is when configuring session manager replication and stateful session bean failover. Using one replication domain in this case ensures that the backup state information of HTTP sessions and stateful session beans are on the same appservers.
Partial partitioning Configure partial partitioning. Partition the replication domain to filter the number of processes to send data. Partial partitioning is deprecated. When using data replication domains, we can specify a specific number of replicas for each entry. However, if we specify a number of replicas larger than the number of backup application servers that are running, the number of replicas is the number of application servers that are running. After the number of appservers increases above the configured number of replicas, the number of replicas that are created is equal to the number specified.
Domain sharing Multiple data replication service (DRS) instances share multi-broker domains. A limitation exists on the number of multi-broker domains that we can create because every multi-broker domain contains at least one replicator. A maximum of one replicator can be on each appserver. All DRS instances in a replication domain use the same mode. Each replication domain must contain either client only and server only instances, or client and server instances only. For example, if one instance is configured to client and server, all other instances must be client and server. If one instance in a replication domain is configured to be a client only, we can add client only and server only instances, but not a client and server instance.

Related concepts
Replication

Related tasks
Replicating data across appservers in a cluster
Migrate servers from multi-broker replication domains to data replication domains

	Version 5.x appservers using replication domains	V6.x and V7.0 appservers using replication domains
Replication domain types	Uses only multi-broker replication domains for replication.	Servers that are using the current version of WAS can be configured to use both multi-broker replication domains and data replication domains for replication. The two types of domains provide backward compatibility with multi-broker domains that were created with a V5.x server. You should migrate any multi-broker domains to data replication domains.
Data transport method	Uses multi-broker domain objects that contain configuration information for the internal JMS provider, which uses JMS brokers as replicators.	Uses data replication domain objects that contain configuration information to configure the high availability framework on WAS ND. The transport is no longer based on the JMS API. Therefore, no replicators and no JMS brokers exist. You do not have to perform the complex task of configuring local, remote, and alternate replicators. The earlier version of WAS did not support data replication domains. The current version of WAS can be configured to perform replication using old multi-broker domains by ignoring any JMS-specific configuration and by using the other parameters to configure replication through the high availability framework.
Replication domain configuration	The earlier version of WAS encourages the sharing of replication domains between different consumers, such as session manager and dynamic cache.	The current version of WAS encourages creating a separate replication domain for each consumer. For example, create one replication domain for session manager and another replication domain for dynamic cache. The only situation where you should configure one replication domain is when configuring session manager replication and stateful session bean failover. Using one replication domain in this case ensures that the backup state information of HTTP sessions and stateful session beans are on the same appservers.
Partial partitioning	Configure partial partitioning. Partition the replication domain to filter the number of processes to send data.	Partial partitioning is deprecated. When using data replication domains, we can specify a specific number of replicas for each entry. However, if we specify a number of replicas larger than the number of backup application servers that are running, the number of replicas is the number of application servers that are running. After the number of appservers increases above the configured number of replicas, the number of replicas that are created is equal to the number specified.
Domain sharing	Multiple data replication service (DRS) instances share multi-broker domains. A limitation exists on the number of multi-broker domains that we can create because every multi-broker domain contains at least one replicator. A maximum of one replicator can be on each appserver.	All DRS instances in a replication domain use the same mode. Each replication domain must contain either client only and server only instances, or client and server instances only. For example, if one instance is configured to client and server, all other instances must be client and server. If one instance in a replication domain is configured to be a client only, we can add client only and server only instances, but not a client and server instance.