Cache Fusion in RAC

What is Cache Fusion in RAC? || GRD (Global Resource Directory) || GCS and GES Background Process

Oracle RAC transfers data blocks from the buffer cache of one instance to the buffer cache of another instance across the cluster interconnect
Advantages:
- No I/O activity
- Data blocks transfer via private N/W – cluster interconnect N/W
- Performance Improvement

In RAC Internodes-Synchronization is very important
Which will prevent the changing the same block by 2 different connections
Internode-Synchronization guarantee that each instance sees the most recent version of the block

1. Cluster required synchronization among the cluster nodes

2. RAC uses GRD – Global Resource Directory to record how the resource are used within the cluster

GCS – Global Cache Service
GES – Global Enqueues Service

3. GCC & GES manages the information in GRD

4. Each Instance manages part of GRD in its SGA

5. GCS and GES nominate the master node to manage the all the information in GRD

6. Each instance know who is master and which instance has what resource

7. Cache Coherency – Keeping the data blocks consistent across the cluster nodes

8. GCS implements this cache coherency by technic called Cache Fusion algorithm

GES:
- dictionary cache locks
- library cache locks
- dead locks

#CacheFusion #GRD #GCS #GES #Clusterware #ClusterMasterNode #Database #Exadata #RAC #ASM #Oracle

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