本文转自:EXAFUSION - FAQ (文档 ID 2037900.1)

Applies to:

Purpose

This document describes the Frequently Asked Questions on Exafusion and the EXAFUSION_ENABLED parameter.

Questions and Answers

What is Exafusion

Exafusion is Direct-to-Wire protocol allows database processes to read and send Oracle Real Applications Cluster (Oracle RAC) messages directly over the Infiniband network bypassing the overhead of entering the OS kernel,and running the normal networking software stack. This improves the response time and scalability of the Oracle RAC environment on Oracle Exadata Database Machine. Data is transferred directly from user space to the Infiniband network,leading to reduced cpu utilization and better scale-out performance. Exafusion is especially useful for OLTP applications because per message overhead is particularly apparent in small OLTP messages.

Exafusion helps small messages by bypassing OS network layer overhead.

What is the pre-requisite for Exafusion

Oracle Exadata Storage Server Software release 12.1.2.1.1 or later.
Oracle Database software Release 12.1.0.2.0 BP11 or later.

Mellanox ConnectX-2 and ConnectX-3 Host Channel Adapters (HCAs) are required.
Oracle Enterprise Kernel 2 Quarterly Update 5 (UEK2QU5) kernels (2.6.39-400.2nn) or later are required.

How to Enable Exafusion

Exafusion is disabled by default.

To enable Exafusion,set the EXAFUSION_ENABLED initialization parameter to 1.

To disable Exafusion,set the EXAFUSION_ENABLED initialization parameter to 0.

This parameter cannot be set dynamically. It must be set before instance startup.

All of the instances in an Oracle RAC cluster must enable this parameter,or all of the instances in an Oracle RAC cluster must disable the parameter.

Known Issues

After upgrading database,users are not able to connect to the database from their OS login where as the same users are able to connect from ORACLE OS user. It returns the following error while connecting:

ERROR: ORA-00600: internal error code,arguments: [ipc_create_que_1],[2],[8],[],[]

This is caused by running EXAFUSION_ENABLED=1 on an unsupported version - lower than Exadata 12.1.0.2 BP 11.

References