B.4.2 Changing Kernel Parameter Values

Use these instructions to display and change the kernel parameter values if they are different from the minimum recommended value.

Use the following commands to display the current values of the kernel parameters:

Table B-4 Commands to Display Kernel Parameter Values

Parameter Command
semmsl, semmns, semopm, and semmni # /sbin/sysctl -a | grep sem

This command displays the value of the semaphore parameters in the order listed.

shmall, shmmax, and shmmni # /sbin/sysctl -a | grep shm

This command displays the details of the shared memory segment sizes.

file-max # /sbin/sysctl -a | grep file-max

This command displays the maximum number of file handles.

ip_local_port_range # /sbin/sysctl -a | grep ip_local_port_range

This command displays a range of port numbers.

rmem_default # /sbin/sysctl -a | grep rmem_default
rmem_max # /sbin/sysctl -a | grep rmem_max
wmem_default # /sbin/sysctl -a | grep wmem_default
wmem_max # /sbin/sysctl -a | grep wmem_max
aio-max-nr # /sbin/sysctl -a | grep aio-max-nr

If you used the Oracle Preinstallation RPM to complete you preinstallation configuration tasks, then the Oracle Preinstallation RPM sets these kernel parameters for you. However, if you did not use the Oracle Preinstallation RPM or the kernel parameters are different from the minimum recommended value, then to change these kernel parameter values:

  1. Using any text editor, create or edit the /etc/sysctl.d/97-oracle-database-sysctl.conf file, and add or edit lines similar to:
    fs.aio-max-nr = 1048576
    fs.file-max = 6815744
    kernel.shmall = 2097152
    kernel.shmmax = 4294967295
    kernel.shmmni = 4096
    kernel.sem = 250 32000 100 128
    net.ipv4.ip_local_port_range = 9000 65500
    net.core.rmem_default = 262144
    net.core.rmem_max = 4194304
    net.core.wmem_default = 262144
    net.core.wmem_max = 1048576
    By specifying the values in the /etc/sysctl.d/97-oracle-database-sysctl.conf file, the values persist on system restarts.
  2. To change the current values of the kernel parameters:
    # /sbin/sysctl --system
    Review the output. If the values are incorrect, edit the /etc/sysctl.d/97-oracle-database-sysctl.conf file, then enter this command again.
  3. Confirm that the values are set correctly:
    # /sbin/sysctl -a
  4. Restart the computer, or run sysctl --system to make the changes in the /etc/sysctl.d/97-oracle-database-sysctl.conf file available in the active kernel memory.
Guidelines for Setting Kernel Parameter Values
  • If you used the Oracle Preinstallation RPM, then your kernel parameter settings reside in the /etc/sysctl.d/99-oracle-database-server-18c-preinstall-sysctl.conf file.

  • Include lines only for the kernel parameter values to change. For the semaphore parameters (kernel.sem), you must specify all four values. If any of the current values are larger than the minimum value, then specify the larger value.

  • The /etc/sysctl.conf file has been deprecated.

  • Avoid setting kernel parameter values in multiple files under /etc/sysctl.d/. The file with a lexically later name under /etc/sysctl.d/ takes precedence, followed by /etc/sysctl.conf. Oracle recommends that you use the Oracle Preinstallation RPM which, among other preinstallation tasks, also sets the kernel parameter values for your database installation.

    See Also:

    sysctl.conf(5) and sysctl.d(5) man pages for more information