Oracle AIX RAC User Datagram Protocol

Oracle RAC clusters on AIX have the User Datagram Protocol (UDP) to manage inter-process communications, and the UDP kernel settings should be tuned to improve Oracle process-level performance.

The IBM document "Configuring IBM System Storage DS4000 Series For Oracle Database Applications" (October 2007) notes:

You can adjust the UDP kernel settings with the network options (no) command, which can alter the udp_sendspace and udp_recvspace parameters.

Set the value of the udp_sendspace parameter to [(DB_BLOCK_SIZE *DB_FILE_MULTIBLOCK_READ_COUNT) + 4096], but not less than 65536.

Set the value of the udp_recvspace parameter to be >= 4 * udp_sendpace

If necessary, increase sb_max parameter (default value is 1048576), since sb_max must be >= udp_recvspace

The value of the udp_recvspace parameter should be at least four to ten times the value of the udp_sendspace parameter because UDP might not be able to send a packet to an application before another packet arrives.

To determine the suitability of the udp_recvspace parameter settings, enter the following command:

netstat -s | grep “socket buffer overflows”