Oracle Application Server provides redundancy by offering support for multiple instances supporting the same workload. These redundant configurations provide increased availability either through a distributed workload, through a failover setup, or both. From the entry point to an Oracle Application Server system (content cache) to the back end layer (data sources), all the tiers that are crossed by a request can be configured in a redundant manner with Oracle Application Server. The configuration can be an active-active configuration using OracleAS Cluster or an active-passive configuration using OracleAS Cold Failover Cluster.
In an OracleAS Cluster, two or more Oracle Application Server instances are configured to serve the same application workload. These instances can reside on the same machine or on different machines.The active instances may be front-ended by an external load balancer, which can redirect requests to any of the active instances, or by some other application-level configuration, such as address lists, to distribute the requests. To load balance requests among many Oracle Application Server instances in an active-active configuration, Oracle recommends the use of an external load balancer.
Brocade ServerIron, a network-centric hardware load balancer and application delivery controller provides the necessary capabilities to enable resilient Oracle AS infrastructures.
Here is sample architecture with Brocade ServerIron providing a resilient, high performance HA load balancing for an Oracle OAS infrastructure. With respect to OAS intances, we are reference load balancing of OHS (Oracle HTTP server), OC4J (Containers) J2EE , Oracle Forms, Oracle Reports, Oracle Portal, SSO (Single Sign On) , OID, (Oracle Identify Directory), DAS (Delegated Administration Service) and OAM (Oracle Access Manager) . OHS load balancing can occur in Mid-tier or Infra Tier.
ServerIron can be configured in several designs to enable highly available OracleAS deployments. To recap, ServerIron offers layer 4-7 application traffic management and web optimization capabilities in a dedicated network-centric hardware platform. These devices provide server load balancing, application aware server health checking, layer 7 content switching, cookie persistence and global load balancing across multiple sites.
It efficiently distributes client requests to the "best" server or OAS instance in the pool by considering server availability, load, response time, and other server selection performance metrics to provide the best end-user response time and availability. Using application-specific "health checks" to servers and applications, ADCs identify unavailable resources in real time and switch users to available servers. They also help scale server farms on demand by adjusting server capacity without impacting application availability. When more capacity is needed, a new server or application instance can be added to the pool without adversely impacting the end user
With integration of SSL hardware, ServerIron can terminate incoming SSL traffic and accelerate the performance of HTTPS applications by offloading the overhead of SSL processing from the real servers.
Some of the benefits of ServerIron load balancing in a Oracle AS infrastructure could be summed as follows:-
For reference, Here is deployment guide which walks you through configuring a Highly Available OracleAS Infrastructure, specific to load balancing Identify Management components with Brocade ServerIron Application Delivery Controllers,
Sources and useful Reference Material
Oracle® Application Server High Availability Guide http://download.oracle.com/docs/cd/B14099_19/core.1012/b14003/framewk.htm
Oracle AS and ServerIron White Paper: http://www.brocade.com/downloads/documents/white_papers/Oracle_Serveriron_WP_00.pdf
Oracle Identify management: http://www.oracle.com/technology/products/id_mgmt/pdf/idm_tech_wp_11g_r1.pdf