Oracle 19c - Oracle 19c RAC | Real Application Clusters (RAC) Technical Architecture Overview Part4
Part1: https://www.youtube.com/watch?v=nQEn3... Part2: https://www.youtube.com/watch?v=w3Kmx... Part3: https://www.youtube.com/watch?v=sT2mk... Oracle 19c Grid Infrastructure requires certain files and provides tools to access each. Each Standalone Cluster should have a Grid Infrastructure Management Repository (GIMR) installed or be a part of a Domain Service Cluster having a GIMR. In Oracle 19c Grid Infrastructure, the GIMR is not required for a Standalone Cluster but recommended. If the GIMR is not installed and configured several features are not available, such as: Cluser Health Advisor, and Fleet Patching and Provisioning. Oracle Clusterware uses voting files to provide node fencing using the disk storage heartbeat and cluster node membership information. Oracle Cluster Registry (OCR) provides cluster configuration and resource information. Both CRSVTL and SVRCTL will update the cluster resource information in the OCR, and the OLR's as necessary. Collectively, voting files and OCR are referred to as Oracle Clusteware files. Oracle Clusterware files must be stored on Oracle ASM. If the underlying storage for the Oracle ASM disks is not hardware protected, such as RAID, then Oracle recommends that you configure multiple locations for OCR and voting files. OCR: Cluster configuration information is maintained in the OCR. You can have up to five OCR locations. Each OCR location must reside on shared storage that is accessible by all nodes in the cluster. The OCR relies on distributed shared cache architecture for optimizing queries, and clusterwide atomic updates against the cluster repository. Each node in the cluster maintains an in-memory copy of OCR, along with the CRSD that accesses its OCR cache. Only one of the CRSD processes actually reads from and writes to the OCR file on shared storage. This process is responsible for refreshing its own local cache, as well as the OCR cache on other nodes in the cluster. For queries against the cluster repository, the OCR clients communicate directly with the local CRS daemon (CRSD) process on the node from which they originate. When clients need to update the OCR, they communicate through their local CRSD process to the CRSD process that is performing input/output (I/O) for writing to the repository on disk. The main OCR client applications are CRSCTL, OUI, SRVCTL, Enterprise Manager (EM), the Database Configuration Assistant (DBCA), the Database Upgrade Assistant (DBUA), Network Configuration Assistant (NETCA), and the ASM Configuration Assistant (ASMCA). Furthermore, OCR maintains dependency and status information for application resources defined within Oracle Clusterware specifically databases, instances, services, and node applications. Note: In the diagram in the slide, note that a client process might also exist on node 2 but is not shown for the sake of clarity. Cheers! Hope this helps! Ramesh.
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