If you have an OLTP application running on Exadata and frequently updating to adding rows to tables from multiple database blocks, you can take advantage of Smart Fusion Block Transfer capability which uniquely improves performance of a RAC configuration by eliminating the impact of redo log write latency. Especially DML queries running from multiple instances, can lead to hot blocks transfer between Oracle RAC Nodes. This feature can transfer hots blocks as soon as the I/O to the redo log is issued at the sending node, without waiting for it to complete. As per Oracle “It has been observed that Smart Block Transfer increases throughput (about 40% higher) and decreases response times (about 33% less) for communication intensive workloads”.
Without Exadata’s Smart Fusion Block Transfer feature, a hot block can be transferred from a sending node to a receiver node only after the sending node has made changes in its redo log buffer durable in its redo log. With Smart Fusion Block Transfer, this latency of redo log write at the sending node is eliminated. So if you have an OLTP workload where hot blocks need to updates frequently across multiple nodes in RAC, you should looking in enable this feature. This feature is disable by default.
To enable Smart Fusion Block Transfer:
- Set the hidden static parameter “_cache_fusion_pipelined_updates” toTRUE on all Oracle RAC nodes. Because this is a 0 parameter, you need to restart your database for this change to take effect.
- Set the “exafusion_enabled” parameter to1 on all Oracle RAC instances.
This feature is only available on Lunix operating system of Exadata Machine, not supported on SPARC or non-engineered system. This feature also requires Oracle Database 12c Release 1 (126.96.36.199) Bundle Patch 11 (BP11). Enabling this feature on unsupported versions can prevent you starting Oracle instances