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FusionCube DB 3.1 Database Best Practice 03 (Oracle RAC 11g R2)

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Disabling THP

Disabling THP

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

  • Disabling the THP is a risky operation. Restart the node after checking that the parameters are modified in the right place.
  • You are advised not to restart the node after the configuration is complete but after Oracle RAC installation partitions are created in Configuring the Cluster Installation Directory.

Procedure

  1. Check the THP status.

    • If the database node uses Red Hat Enterprise Linux 6, run the following command:
      [root@dbn01~]# cat /sys/kernel/mm/redhat_transparent_hugepage/enabled
      [always] madvise never
    • If the database node uses Red Hat Enterprise Linux 7, run the following command:
      [root@dbn01~]# cat /sys/kernel/mm/transparent_hugepage/enabled
      [always] madvise never

    If "always" is displayed in the command output, THP is enabled.

  2. Add the transparent_hugepage field to the grub.conf file to disable THP.

    • If the database node uses Red Hat Enterprise Linux 6, add "transparent_hugepage=never" to the end of the "kernel..." line in the /etc/grub.conf file.
      [root@dbn01~]# vi  /etc/grub.conf  
      title Red Hat Enterprise Linux 6 (2.6.32-573.el6.x86_64)
              root (hd0,0)
          kernel /vmlinuz-2.6.32-573.el6.x86_64 ro root=UUID=3c544f9b-5f0b-4833-8d46-f4b44ccb538e rd_NO_LUKS KEYBOARDTYPE=pc KEYTABLE=us LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 rd_NO_LVM rhgb quiet rd_NO_DM rhgb quiet memmap=0x2000000$0x3E000000 nmi_watchdog=2 crashkernel=256M-:256M printk.time=1 console=ttyS0,115200 console=tty0 transparent_hugepage=never
              initrd /initramfs-2.6.32-573.el6.x86_64.img ~ 
      Figure 3-3 Editing the /etc/grub.conf file on Red Hat Linux 6
    • If the database node uses Red Hat Enterprise Linux 7, 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 biosdevname=0
      net.ifnames=0 rhgb quiet console=ttyS0,115200 console=tty0
      intel_idle.max_cstate=0 processor.max_cstate=0 transparent_hugepage=never"
      
      Figure 3-4 Edit the/etc/default/grub file on Red Hat Linux 7

      The command used to generate the grub.cfg file varies depending on the boot mode (legacy BIOS or UEFI) of the server. To query the boot mode, log in to the server iBMC WebUI, and choose Configuration > Boot Device.

      NOTE:

      V5 servers use the UEFI mode by default.

      If the UEFI mode is used, run the following command:

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

      If the legacy BIOS mode is used, run the following command:

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

  3. Generate the grub.conf file.
  4. Restart the node for the modification to take effect and check the settings.

    • If the database node uses Red Hat Enterprise Linux 6, run the following command:
      [root@dbn01 ~]# cat /sys/kernel/mm/redhat_transparent_hugepage/enabled
      always madvise [never]
    • If the database node uses Red Hat Enterprise Linux 7, run the following command:
      [root@dbn01 ~]#  cat /sys/kernel/mm/transparent_hugepage/enabled
      always madvise [never]

    If "never" is displayed in the command output, THP is disabled.

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Updated: 2018-12-26

Document ID: EDOC1100035759

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