Oracle Tips by Burleson

Oracle10g Grid Computing with RAC
Chapter 6 - Install, Configure and Database Creation

Interconnect

Another method of finding the protocol is to look into the alert log file of the Oracle instance. During startup, a message is posted showing the IPC details. For example, 

Wed Oct 30 05:28:55 2002
cluster interconnect IPC version: Oracle UDP/IP with Sun RSM disabled
IPC Vendor 1 proto 2 Version 1.0 

Message Size

The message size is platform dependent. In Oracle9i Release 2 (9.2.0.1), message size was limited to 32K. Before 9.2.0.1, the Operating System UDP settings are overwritten and a 32k buffer is used.

Oracle9i allows larger message sizes, depending on the platform. To increase throughput on an interconnect, the UDP kernel parameters must be adjusted.

Oracle opens the UDP receive ports with a receive buffer size of 128k, but it also honors O/S settings and can even adjust the size based on the maximum block size seen, up to the O/S maximum. The operating system maximum for the UDP receive buffer size is: