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KunLun Mission Critical Server Oracle Database Oracle 12c R1 (RAC) Best Practice 02

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Disabling THP

Disabling THP

If the cluster is running on the RHEL kernel, disable the THP (Transparent Huge Pages) feature to prevent nodes and instances from being unexpectedly removed from the cluster.

  • Disabling THP is a risky operation. Verify that the parameters are correctly modified before restarting the node.
  • Perform this operation on each node.
  • If the database node OS is RHEL 6, run the following command to perform a check:

    Run the following command:

    [root@dbn01~]# cat /sys/kernel/mm/transparent_hugepage/enabled
    [always] madvise never

    If "always" is displayed in the command output, run the following command to disable THP and add "transparent_hugepage=never" to the end of the "kernel..." line in the /boot/efi/EFI/redhat/grub.conf file.

    The following uses the RHEL 6.8 default kernel as an example.

    [root@dbn01~]# vi /boot/efi/EFI/redhat/grub.conf
    title Red Hat Enterprise Linux 6 (2.6.32-642.el6.x86_64)
    root (hd0,0)
    kernel /vmlinuz-2.6.32-642.el6.x86_64 ro root=UUID=7b3b7562-f254-4572-8e25-5e49c7a42e37 rd_NO_LUKS rd_NO_LVM LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_NO_DM quiet nowatchdog nosoftlockup rcupdate.rcu_cpu_stall_timeout=600 rcupdate.rcu_cpu_stall_suppress=1 console=tty0 console=ttyS0,115200 transparent_hugepage=never
    initrd /initramfs-2.6.32-642.el6.x86_64.img

    Restart the node and check whether "never" is displayed in the command output.

    [root@dbn01 ~]# cat /sys/kernel/mm/transparent_hugepage/enabled
    always madvise [never]
  • If the database node OS is RHEL 7, run the following command to perform a check:
    [root@dbn01~]# cat /sys/kernel/mm/transparent_hugepage/enabled
    [always] madvise never

    If "always" is displayed in the command output, run the following command to disable THP and add "transparent_hugepage=never" to the end of the "GRUB_CMDLINE_LINUX..." line in the /etc/default/grub file:

    [root@dbn01 ~]# vi /etc/default/grub
    ...
    GRUB_CMDLINE_LINUX="crashkernel=auto rhgb quiet efi=old_map nowatchdog nosoftlockup rcupdate.rcu_cpu_stall_timeout=600 rcupdate.rcu_cpu_stall_suppress=1 hpet=disable pmtmr=0 console=tty0 console=ttyS0,115200 transparent_hugepage=never"
    

    Run the following command to regenerate the grub.cfg configuration file:

    [root@dbn01 ~]# grub2-mkconfig -o /boot/efi/EFI/redhat/grub.cfg

    Restart the node and check whether the configuration is correct.

    [root@dbn01 ~]# cat /sys/kernel/mm/transparent_hugepage/enabled
    always madvise [never]
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Updated: 2019-02-01

Document ID: EDOC1100053123

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