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• 25 Jul, 2025
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RAC Tuning

1. Cluster Interconnect Tuning

• Network Configuration: Ensure that the private interconnect network is configured optimally. Use dedicated, high-speed networks (e.g., 10GbE or Infiniband). 

• Load Balancing: Utilize Oracle’s interconnect load balancing mechanisms to distribute traffic evenly across available network interfaces. 

• UDP Buffer Size: Increase the UDP buffer size to handle increased inter-node communication. 

2. Cache Fusion Tuning

• Global Cache Latency: Minimize global cache latency by optimizing the interconnect and reducing contention on shared resources. 

• Block Transfer Sizes: Use appropriate block transfer sizes to minimize overhead during block transfers between nodes. 

• Instance Affinity: Ensure that sessions or workloads are affinitized to specific nodes to reduce the need for block transfers. 

3. Workload Distribution

• Load Balancing Advisory: Configure the service’s connection load balancing advisory to distribute workload effectively across the cluster. 

• Dynamic Resource Allocation: Use dynamic resource allocation policies to ensure that the system adapts to changing workloads in real-time. 

• Services & Instances: Assign services to specific instances based on workload characteristics. 

4. Storage I/O Tuning

• ASM Configuration: Optimize Oracle ASM (Automatic Storage Management) for better I/O performance by configuring appropriate redundancy and striping policies. 

• I/O Distribution: Ensure that the I/O workload is evenly distributed across all nodes and storage devices. 

• Disk Group Design: Use high-performance storage and configure disk groups for optimal performance. 

5. CPU and Memory Tuning

• CPU Allocation: Ensure proper CPU allocation across all nodes, avoiding CPU bottlenecks on any particular node. 

• Memory Configuration: Tune memory allocation, including the SGA and PGA, to optimize database performance. 

• NUMA Optimization: For NUMA (Non-Uniform Memory Access) systems, ensure that memory access patterns are optimized to reduce latency. 

6. Parallel Execution Tuning

• Parallel Execution Configuration: Optimize parallel execution settings to distribute parallel query execution across nodes effectively. 

• Degree of Parallelism (DOP): Set an appropriate DOP based on the system’s capabilities to maximize performance without overloading resources. 

7. Global Enqueue and Lock Management

• Enqueue Wait Tuning: Reduce enqueue wait events by minimizing contention for shared resources. 

• Lock Management: Ensure that locking mechanisms are efficiently managed to reduce contention and bottlenecks. 

8. SQL Plan Management

• SQL Tuning: Ensure that SQL statements are optimized to reduce resource consumption. Use SQL profiles and baselines to stabilize execution plans. 

• Execution Plans: Monitor execution plans for consistency across nodes, ensuring that RAC-specific issues like inter-node block transfers are minimized. 

9. Diagnostic and Monitoring Tools

• Oracle Enterprise Manager (OEM): Use OEM’s RAC-specific features like the Cluster Database Performance page and Performance Hub to monitor and diagnose performance issues. 

• AWR and ASH Reports: Generate AWR and ASH reports to identify top wait events, SQLs, and areas that need tuning. 

• GV$ Views: Utilize Global V$ views like GV$INSTANCE, GV$SESSION, GV$ACTIVE_SESSION_HISTORY, etc., to gain insights into cluster-wide performance. 

10. Application Tuning

• Session Affinity: Ensure that the application tier is tuned to maintain session affinity, reducing unnecessary block transfers between nodes. 

• Connection Pools: Tune connection pools to distribute connections evenly across instances and ensure efficient utilization of resources.