Red Hat CLUSTER SUITE FOR ENTERPRISE LINUX 5.1, Tuning Manual

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Verifying Kernel Parameters
73
On the following versions of Red Hat Enterprise Linux 4 x86, 3 U5 x86, 3 U5 x86-64, and 2.1; you
may have to increase the kernel parameters
shmmax
,
semopm
, and
filemax
to meet the minimum
requirement. 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 messages
to "1024 65000" which is needed for high usage systems. This kernel parameter defines the local port
range 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=2147483648
kernel.sem=250 32000 100 128
fs.file-max=65536
net.ipv4.ip_local_port_range=1024 65000
Adding these lines to the
/etc/sysctl.conf
file will cause the system to change these kernel
parameters 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
become
effective immediately, execute the following command:
su - root
sysctl -p
For more information on shmmax, shmmni, shmmin, shmseg, and shmall, see
Chapter 7, Setting
Shared 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. 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 the received data for the application until it is read. This buffer cannot overflow
because the sending party 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 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 by
running the following commands: 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.
# sysctl -w net.core.wmem_max=262144