Adjusting Network Settings; Changing Network Adapter Settings; Changing Network Kernel Settings - Red Hat ENTERPRISE LINUX 5.1 - LINUX ORACLE Tuning Manual

Oracle 9i and 10g tuning guide

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Chapter 10.

Adjusting Network Settings

To check the speed and settings of network adapters, use the ethtool command which works now

for most network interface cards. To check the adapter settings of eth0 run:

# ethtool eth0

To force a speed change to 1000Mbps, full duplex mode, run:

# ethtool -s eth0 speed 1000 duplex full autoneg off

To make a speed change permanent for eth0, set or add the ETHTOOL_OPT environment variable in

/etc/sysconfig/network-scripts/ifcfg-eth0:

ETHTOOL_OPTS="speed 1000 duplex full autoneg off"

This environment variable is sourced in by the network scripts each time the network service is

started.

Oracle now uses User Datagram Protocol (UDP) as the default protocol on Linux for interprocess

communication, such as cache fusion buffer transfers between the instances. However, starting with

Oracle 10g network settings should be adjusted for standalone databases as well.

Oracle recommends the default and maximum send buffer size (SO_SNDBUF socket option) and

receive buffer size (SO_RCVBUF socket option) to be set to 256 KB. The receive buffers are used

by TCP and UDP to hold received data until it is read by the application. The receive buffer cannot

overflow because the peer is not allowed to send data beyond the buffer size window. This means that

datagrams will be discarded if they do not fit in the socket receive buffer. This could cause the sender

to overwhelm the receiver.

The default and maximum window size can be changed in the proc file system without reboot:

The default setting in bytes of the socket receive buffer

# sysctl -w net.core.rmem_default=262144

The default setting in bytes of the socket send buffer

# sysctl -w net.core.wmem_default=262144

The maximum socket receive buffer size which may be set by using the SO_RCVBUF socket option

# sysctl -w net.core.rmem_max=262144

The maximum socket send buffer size which may be set by using the SO_SNDBUF socket option

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