Oracle Clusterware is a portable cluster management solution that is integrated with Oracle Database. Oracle Real Application Clusters (Oracle RAC) uses Oracle clusterware as the infrastructure that binds together multiple nodes which operate as a single server. Oracle Clusterware includes a high availability framework for managing any application that runs on your cluster. Voting disk and the OCR is created on shared storage during Oracle Clusterware installation process.
The Oracle Clusterware includes two important components: the voting disk and the Oracle Cluster Registry (OCR). The voting disk is a file that manages information about node membership and the OCR is a file that manages cluster and Oracle Real Application Clusters (Oracle RAC) database configuration information.
1. Voting Disk: - Manages cluster membership by way of a health check and arbitrates cluster ownership among the instances in case of network failures. RAC uses the voting disk to determine which instances are members of a cluster. The voting disk must reside on shared disk. For high availability, Oracle recommends that you have multiple voting disks. The Oracle Cluster ware enables multiple voting disks.
Note:- If you define a single voting disk, then you should use external mirroring to provide redundancy.
2. OCR File :- Cluster configuration information is maintained in Oracle Cluster Registry file. OCR relies on a distributed shared-cache architecture for optimizing queries against the cluster repository. Each node in the cluster maintains an in-memory copy of OCR, along with an OCR process that accesses its OCR cache.
When OCR client application needs to update the OCR, they communicate through their local OCR process to the OCR process that is performing input/output (I/O) for writing to the repository on disk.
The OCR client applications are Oracle Universal Installer (OUI), SRVCTL, Enterprise Manger (EM), Database Configuration Assistant (DBCA), Database Upgrade Assistant(DBUA), NetCA and Virtual Internet Protocol Configuration assistant (VIPCA). OCR also maintains dependency and status information for application resources defined within CRS, specifically databases, instances, services and node applications.
Note:- The name of the configuration file is ocr.loc and the configuration file variable is ocrconfig.loc
Oracle Cluster Registry (OCR) :- Maintains cluster configuration information as well as configuration information about any cluster database within the cluster. The OCR also manages information about processes that Oracle Clusterware controls. The OCR stores configuration information in a series of key-value pairs within a directory tree structure. The OCR must reside on shared disk that is accessible by all of the nodes in your cluster. The Oracle Clusterware can multiplex the OCR and Oracle recommends that you use this feature to ensure cluster high availability.
Note:- You can replace a failed OCR online, and you can update the OCR through supported APIs such as Enterprise Manager, the Server Control Utility (SRVCTL), or the Database Configuration Assistant (DBCA
Want to know more about Real Application Cluster Click Oracle Real Application Cluster
No comments:
Post a Comment