#ORACLE DATABASE 12C UPDATE#

Log in as oracle user again and run the ulimit -l command to verify the new memlock setting: You can also set the memlock value higher than your SGA requirements. For example, if you have 64 GB RAM installed, then add the following entries to increase the maximum locked-in-memory address space: The memlock setting is specified in KB, and the maximum locked memory limit should be set to at least 90 percent of the current RAM when HugePages memory is enabled and at least 3145728 KB (3 GB) when HugePages memory is disabled. CONFIG_HUGETLBFS is located under File Systems and CONFIG_HUGETLB_PAGE is selected when you select CONFIG_HUGETLBFS.Д®dit the memlock setting in the /etc/security/nf file. For such systems, build the Linux kernel using the CONFIG_HUGETLBFS and CONFIG_HUGETLB_PAGE configuration options. Some Linux systems do not support HugePages by default. Run the following command to determine if the kernel supports HugePages: Less bookkeeping work for the kernel for that part of virtual memory because of larger page sizesД¬omplete the following steps to configure HugePages on the computer: Pages are locked in memory and never swapped out, which provides RAM for shared memory structures such as SGAД¬ontiguous pages are preallocated and cannot be used for anything else but for System V shared memory (for example, SGA) Increased performance through increased TLB hits HugePages provides the following advantages: If you do not use HugePages, and you want to map 256 MB of memory, then you must have 256 MB * 1024 KB/4 KB = 65536 PTEs. For example, if you use HugePages with 64-bit hardware, and you want to map 256 MB of memory, you may need one page table entry (PTE). With HugePages, the operating system page table (virtual memory to physical memory mapping) is smaller, because each page table entry is pointing to pages from 2 MB to 256 MB.ДЄlso, the kernel has fewer pages whose lifecycle must be monitored.

#ORACLE DATABASE 12C UPDATE#

When it allocates pages to the database System Global Area (SGA), the operating system kernel must continually update its page table with the page lifecycle (dirty, free, mapped to a process, and so on) for each 4 KB page allocated to the SGA. Without HugePages, the operating system keeps each 4 KB of memory as a page.

Oracle database 12c