As Published In
Oracle Magazine
July/August 2008


High Availability on Linux

By Rich Schwerin

Oracle Clusterware protects mission-critical applications from downtime.

Clustering—grouping independent servers to cooperate as a single system—helps prevent downtime caused by system failure by removing the single point of failure inherent with a single server. Cluster management software is integral to clustering, and Oracle Clusterware, cluster management software previously available only with Oracle Real Application Clusters (Oracle RAC), is now available under a separate license to Unbreakable Linux support customers at the basic and premier levels at no additional cost.

"Oracle Clusterware for Unbreakable Linux can be used both for Oracle and non-Oracle applications," says Sohan DeMel, senior director of product management, Oracle. Oracle Clusterware provides out-of-the-box agents and scripts for select applications; for example, customers can use a prepackaged SAP agent to ensure high availability for their critical SAP resources. This agent alleviates the need for the customer to write scripts for the orchestration of SAP resource failover.

And since all Oracle RAC on Linux customers already use Oracle Clusterware, it makes sense for them to extend that same technology to protect all of their applications from downtime, DeMel says. "Customers shouldn't have to learn and operate one clustering technology for their database and another for their applications. Why not just use one proven technology?"

Cluster Management

As a cluster database technology, Oracle RAC requires a cluster manager for certain management and monitoring functions, and Oracle Clusterware provides these functions. In an Oracle RAC environment, Oracle Clusterware manages all of the Oracle processes automatically, and anything that it manages—databases, instances, services, listeners, application processes—is known as a cluster resource. If a server fails, Oracle Clusterware automatically restarts all the cluster resources and the application service is restored—often before the administrator notices it was down.

In addition to providing an infrastructure to prevent downtime, Oracle Clusterware provides tools and utilities to easily monitor and manage applications and clusters for high availability.

"Oracle Clusterware leverages the management capabilities of Oracle Enterprise Manager, which includes interfaces for managing both single instance and Oracle RAC database environments," says DeMel. "Plus, several command-line tools are available to manage Oracle Clusterware environments. These tools handle everything from verifying the health of components such as shared storage and network interfaces and administering resources under cluster management to expanding or shrinking the cluster."

High-Availability Grids

Next Steps

 DOWNLOAD Oracle Clusterware for Oracle Unbreakable Linux

 LEARN more about Oracle Unbreakable Linux

Oracle Clusterware provides unique benefits such as support for up to 100 nodes in a single cluster and rolling upgrades of the cluster manager software. Oracle Clusterware is the ideal cluster infrastructure in enterprise grid environments, explains DeMel. "It provides benefits in the areas of high availability, database consolidation, and storage consolidation. In addition to standard application failover technology, Oracle Clusterware provides the capability to model critical resources and their associated dependencies and orchestrate failovers based on those dependencies," he says.

Increasingly, customers are using Oracle Clusterware as a platform to consolidate their databases and associated storage, managed with Oracle Automatic Storage Management. "Consolidating multiple databases onto a single clusterwide storage pool managed via Oracle Automatic Storage Management has tremendous benefit with regard to increasing application performance and storage utilization," DeMel says.

"Oracle Clusterware is by far the most widely deployed cluster manager on Linux today," concludes DeMel. "It's the smart choice for customers who need a single high-availability technology to protect all their applications."

Rich Schwerin ( is the Linux, virtualization, and open source senior product marketing manager with Oracle technology marketing.

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