Verifying Kernel Parameters73On the following versions of Red Hat Enterprise Linux 4 x86, 3 U5 x86, 3 U5 x86-64, and 2.1; youmay have to increase the kernel parameters shmmax, semopm, and filemax to meet the minimumrequirement. On Red Hat Enterprise Linux 4 x86-64 you may have to increase shmmax and semopm.Oracle also recommends to set the local port range ip_local_port_range for outgoing messagesto "1024 65000" which is needed for high usage systems. This kernel parameter defines the local portrange for TCP and UDP traffic to choose from.In order to meet these requirements, you may have to add the following lines to the /etc/sysctl.conf file which are read during the boot process:kernel.shmmax=2147483648kernel.sem=250 32000 100 128fs.file-max=65536net.ipv4.ip_local_port_range=1024 65000Adding these lines to the /etc/sysctl.conf file will cause the system to change these kernelparameters after each boot using the /etc/rc.d/rc.sysinit script which is invoked by /etc/inittab. But in order that these new added lines or settings in /etc/sysctl.conf becomeeffective immediately, execute the following command:su - rootsysctl -pFor more information on shmmax, shmmni, shmmin, shmseg, and shmall, see Chapter 7, SettingShared Memory. For more information on semmsl, semmni, semmns, and semopm, see Chapter 24,Creating Oracle Directories. For more information on filemax, see Chapter 9, Setting File Handles.Starting with 10g R2 some network settings must be adjusted as well which is checked by OUI. Oraclerecommends the default and maximum send buffer size (SO_SNDBUF socket option) and receivebuffer size (SO_RCVBUF socket option) to be set to 256 KB. The receive buffers are used by TCPand UDP to hold the received data for the application until it is read. This buffer cannot overflowbecause the sending party is not allowed to send data beyond the buffer size window. This meansthat datagrams will be discarded if they do not fit in the receive buffer. This could cause the sender tooverwhelm the receiver.The default and maximum window size can be changed in the proc file system without reboot byrunning the following commands: The default setting in bytes of the socket receive buffer.# sysctl -w net.core.rmem_default=262144The default setting in bytes of the socket send buffer.# sysctl -w net.core.wmem_default=262144The maximum socket receive buffer size which may be set by using the SO_RCVBUF socket option.# sysctl -w net.core.rmem_max=262144The maximum socket send buffer size which may be set by using the SO_SNDBUF socket option.# sysctl -w net.core.wmem_max=262144
