Installing Oracle Linux - Expert Consolidation in Oracle Database 12c - page 166

Table 5-3. ( continued )

Kernel
parameter

Recommended
(minimum) value

Description

shmmni 4096 This parameter sets maximum number of shared memory

segments permissible. This value comes to play in two
different ways: first of all if you set shmmax to a small value
and Oracle has to break down the SGA into smaller pieces.
Secondly, each time an Oracle instance-ASM and RDBMS-is
started, the available number is decremented by one.

The value of 4096 recommended in the Oracle installation
guides guarantees that you will not run out of shared
memory segments.

shmall 1073741824 This parameter determines the system-wide limit on the

total number of pages of shared memory. It should be set to
shmmax/`getconf PAGE_SIZE.

file-max 6815744 This parameter allows you to set a maximum number of

open files for all processes, system-wide. The default should
be sufficient for most systems.

ip_local_port_range 9000 65500 The local port range to be used for Oracle (dedicated) server

processes should be configured to 9000 to prevent a clash
with non-oracle operating system services using the port
numbers as defined in /etc/services .

By lowering the boundary to 9000 you should have enough
ephemeral ports for your expected workload.

rmem_default 262144 This sets the default receive buffer size (in bytes) for all types

of connections-TCP and UDP.

rmem_max 4194304 This sets the maximum receive buffer size (in bytes) for all

connections-TCP and UDP.

wmem_default 262144 This sets the default send buffer size (in bytes) for all types of

connections-TCP and UDP.

wmem_max 1048576 This sets the max OS send buffer size for all types of

connections.

aio-max-nr 1048576 This parameter is related to asynchronous I/O model in

Linux as defined by libaio and should be set to 1048576 to
prevent processes receiving errors when allocating internal
AIO-related memory structures.

The values in Table 5-3 are all listed in /proc/sys/kernel/sem and are responsible for controlling the
semaphores in a Linux system. Oracle uses shared memory and semaphores extensively for inter-process
communication. In simple terms, semaphores are mainly required by processes to attach to the SGA and to control
serialization. The values shown in Table 5-3 should be sufficient for most workloads.