IBM i series Handbook page 510

Operating System/400 (5722-SS1)
customer separately managed the systems in the cluster. Database replication was provided
by high-availability business partner solutions.
V4R4 introduced iSeries Logical Partitioning (LPAR) to enhance the role of the iSeries as a
consolidated server. With LPAR, companies have both the power and flexibility to address
multiple system requirements in a single machine. LPAR is of value to customers that need
server consolidation, business unit consolidation, mixed production, and a test environment,
as well as integrated clusters.
iSeries clusters enable you to set up an environment to provide availability beyond 99.94%
for critical applications and critical data. iSeries server high availability business partners and
ISVs complete the solution with easy-to-use cluster management, robust data resiliency, and
resilient applications that take advantage of the new technology.
Cluster Resource Services consists of an open set of APIs that provide cluster facilities.
iSeries application providers and customers use the APIs to enhance their application
availability and to create, configure, and administer the cluster. Systems are defined into the
cluster as cluster nodes. Communication interface addresses are defined to form the cluster
node-to-node interconnection links. Resilient resources (objects replicated to one or more
nodes) are associated with a Cluster Resource Group (CRG) so they can be managed as a
single unit.
Two types of CRGs are supported: one for data resilience and one for application resilience.
Data CRGs provide the control to switch the point of access for a set of data to a backup
node that maintains an exact replica of that data. Application CRGs control switching an IP
address representing the application server to a backup node and restart the application in
the event of a primary node failure.
Cluster Resource Services include integrated facilities such as heartbeat monitoring, reliable
message delivery, switch-over administration, and distributed activities. The services are built
on a robust cluster topology and messaging functions to keep track of each node in the
cluster and ensure that all nodes have consistent information about the state of cluster
resources.
Heartbeat monitoring ensures that each node is active. When the heartbeat for a node fails,
the condition is reported so that the cluster can automatically failover to the resilient
resources on the backup node. System Services for high availability solutions are enhanced
with real-time recording of IFS stream file changes into journals. Data resiliency applications
can use this function to provide enhanced support for this class of objects.
IBM works closely with the cluster middleware business partners to provide easy-to-use
cluster management applications, among them are: DataMirror, Lakeview Technology, and
Vision Solutions.
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iSeries Handbook