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

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Configuring HugePages

Configuring HugePages

The HugePages feature enables larger page sizes. This feature locks the SGA into the physical memory. Therefore, the SGA system page table does not need to be searched. This feature reduces management expenses and is important especially when a large portion of memory is allocated. For Oracle RAC 11g R1 or later, disable the AMM before enabling HugePages.

After the HugePages parameters are applied, the memory space is immediately allocated and occupied. Ensure that the parameters are correct. If the number is too large, all system memory will be occupied and the node OS will become abnormal.

Perform the following operations on each database node.


  1. Check whether the huge page memory size in the current system is 2048 KB (2 MB).

    [root@dbn01~]# cat /proc/meminfo |grep Hugepagesize
    Hugepagesize: 2048 kB

  2. Calculate the value of vm.nr_hugepages.

    The value of vm.nr_hugepages is calculated as follows: vm.nr_hugepages = sga_max_size + 2 GB. sga_max_size indicates the memory capacity allocated to the SGA. The method for calculating the value of sga_max_size is described in 1.2.2 Oracle RAC Node Memory Plan. The complete formula is as follows:

    vm.nr_hugepages = (node physical memory x 0.65 x 0.75 + 2) x 1024 //Huge page memory size

    If the physical memory size is 512 GB and the unit of the huge page memory size is MB, the calculation method is as follows:

    vm.nr_hugepages = (512 GB x 0.65 x 0.75 + 2) x 1024/2 MB = 128819.2 (pages)

  3. Add the following content to the end of the /etc/sysctl.conf file:

    [root@dbn01~]# vi /etc/sysctl.conf
    vm.nr_hugepages= 128819

  4. Save the configuration, run the following commands for the configuration to take effect, and check whether the configuration is effective:

    [root@dbn01~]# sysctl -p
    [root@dbn01~]# sysctl -a|grep nr_hugepages
    vm.nr_hugepages = 128819
    vm.nr_hugepages_mempolicy = 128819

    If the configuration is not effective, restart the database node OS.

Updated: 2019-02-01

Document ID: EDOC1100053123

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