Introduction to Oracle Clusterware Cluster Ready Services and Oracle Fusion Middleware

13 Using Oracle Cluster Ready Services 13-1 13 Using Oracle Cluster Ready Services This chapter describes conceptual information as well as configuration procedures for Oracle Cluster Ready Services. It contains the following sections: ■ Section 13.1, Introduction to Oracle Clusterware ■ Section 13.2, Cluster Ready Services and Oracle Fusion Middleware ■ Section 13.3, Installing and Configuring Oracle Clusterware with CRS ■ Section 13.4, Using ASCRS to Manage Resources ■ Section 13.5, Example Topologies ■ Section 13.6, Troubleshooting Oracle CRS

13.1 Introduction to Oracle Clusterware

Oracle Clusterware manages the availability of user applications and Oracle databases in a clustered environment. In an Oracle Real Application Clusters Oracle RAC environment, Oracle Clusterware manages all of the Oracle database processes automatically. Anything managed by Oracle Clusterware is known as a cluster resource, which could be a database instance, a listener, a virtual IP VIP address, or an application process. Oracle Clusterware was initially created to support Oracle RAC. Its benefits, however, are not limited to Oracle RAC; it can also be used to manage other applications through add-on modules or action scripts. It is this flexibility and extensibility in Oracle Clusterware that forms the basis of a high availability solution for Oracle Fusion Middleware. For more information about Oracle Clusterware, see the Oracle Clusterware Administration and Deployment Guide.

13.2 Cluster Ready Services and Oracle Fusion Middleware

Oracle Clusterware includes a high availability framework that offers protection to any resource with the help of resource-specific add-on modules. In Oracle Clusterware terminology, a resource refers to an object that is created by Oracle Clusterware to identify the entity to be managed, such as an application, a virtual IP or a shared disk. Oracle Clusterware monitors a resource to make sure it is always available by frequently checking its state, and attempting to restart it if it is down. If restarting fails, the resource will be started on a new node, a process called failover. Resource switchover, an intentional switch of the operating environment of resources, is also allowed through the proper user interface. 13-2 Oracle Fusion Middleware High Availability Guide With this high availability framework, Oracle Clusterware manages resources through user-provided add-on modules. For example, to create a resource for an application running in a single process, a module has to be supplied by the user to start and stop the process, and check its state. If this application fails, Oracle Clusterware attempts to restart it using this module. If the node on which this application is currently running fails, Oracle Clusterware attempts to restart it on another node if the application and resource are configured properly. You can configure the monitoring frequency for a resource and define its relationships to other resources. Application Server Cluster Ready Services ASCRS relieves you from writing your own add-on modules for your critical and complex Oracle Fusion Middleware application environment, thereby giving you easy access to Oracle Clusterwares high availability features. ASCRS consists of a frontend and a backend. The frontend is a command line interface, ascrsctl, with which you can perform administrative tasks, such as resource creation, deletion, update, start, stop or switchover between cluster nodes. The backend is logic for the life cycle management of the various Fusion Middleware resources. The frontend and backend have their own separate log files. On Unix platforms and Windows Server 2008, ASCRS supports virtual IPs, shared disks, database listeners, database instances, OPMN managed instances, and WebLogic servers. You can create Oracle Clusterware resources from these middleware components, allowing Oracle Clusterware and ASCRS to maintain their high availability within the cluster. Oracle Clusterware and ASCRS provide a means to improve the survivability of the various resources when their hosting environment is corrupted or lost. However, they do not prevent disk corruption or application malfunctioning caused by disk corruption. ASCRS supports Oracle Clusterware version 10.2.0.4 or 11.1.0.7 and higher. It has online help that can be invoked using the following command: ascrsctl help -c command -t resource_type As an example, the following command shows the help for creating a virtual IP resource: ascrsctl help -c create -t vip To view the full contents of ascrsctl online help, see Appendix E, ascrsctl Online Help.

13.3 Installing and Configuring Oracle Clusterware with CRS