Restrictions for HugePages and Transparent HugePages Configurations

Review the HugePages and Transparent HugePages guidelines discussed in this section.

For optimal performance, Oracle recommends that you set Transparent HugePages to madvise on all Oracle Database servers UEK7 and later kernels and not disable Transparent HugePages as was recommended in prior releases.

Oracle continues to recommend using standard HugePages for Linux.

Transparent HugePages memory is enabled by default with Oracle Linux 6 and later, Red Hat Enterprise Linux 6 and later, SUSE 11 and later, kernels.

If you install Oracle Database Preinstallation RPM, then it sets Transparent HugePages to madvise on all Oracle Database servers UEK7 and later kernels.

Transparent Hugepages are similar to standard HugePages. However, while standard HugePages allocate memory at startup, Transparent Hugepages memory uses the khugepaged thread in the kernel to allocate memory dynamically during runtime, using swappable HugePages.

HugePages allocates non-swappable memory for large page tables using memory-mapped files. HugePages are not enabled by default. If you enable HugePages, then you should deduct the memory allocated to HugePages from the available RAM before calculating swap space. Refer to your distribution documentation and to Oracle Technology Network and My Oracle Support for more information.