Exadata Exafusion

Exafusion is a Direct-To-Wire protocol which helps database processes to read and send message to other nodes across the cluster. Exafusion in Exadata and cache fusion is non-Exadata is same however the basic difference between both of them is that cache fusion uses UDP to transfer data across the cluster using cluster interconnect however exafusion relies on internal InfiniBand network to work.

 

How EXAFUSION Is Better Than Cache Fusion

Exafusion uses Direct-To-Wire protocol to transfer data over the InfiniBand network which means that it by passes the overhead of entering OS kernel and running the normal networking software stacks which helps RAC in Exadata to transfer data across the cluster if required and boost database performance. Exafusion feature is especially useful for OLTP workload.

                        Pre-Requisite for Exafusion in Exadata

(1)  Exadata storage server software must be running in 12.1.2.1.1 or later

(2)  Database must be running in 12.1.0.2.0 or later.

                     How To Enable Exafusion in Exadata

(1)  In Oracle database 18c or later version, exafusion is enabled by default and we can’t disable  it.

(2)  In Oracle Database 12.2, Exafusion is enabled by default and setting exafusion_enabled=0 will disable the exafusion feature.

(3)  In Oracle Database 12.1, Exafusion is disabled by default and setting exafusion_enabled=1 will enable the exafusion feature in 12.1.

 

NOTE 1: Exafusion_enabled parameter is obsolete from 18.3 onward.

 

NOTE 2: Oracle database 12.1 doesn’t recommend to enable exafusion.

 

                How To Change Exafusion_enabled parameter

(1)  Exafusion_enabled parameter is a static parameter

(2)  The value of exafusion_enabled parameter must be same at all the instances across the cluster.

 (3)   It cannot be set in a rolling manner we must have to bring down all the instances and make the require changes.

 

               Validate If Exafusion is Enable or Not

 

To validate if Exafusion is enabled in 12.2 or higher version we can check the alert log and search for Exafusion value. We’ll get the output like below if exafusion is enable

               Exafusion Value in Alert Log

 

KSIPC Available Transports for cluster communication RC:RDS:UDP:XRC:TCP:UD_RDS

KSIPC Available Transports for storage communication RC:RDS:UDP:XRC:TCP:UD_RDS

KSIPC:  Client:  KCL    Transport:    XRC

KSIPC:  Client:  DLM  Transport:    RDS

Exafusion enabled