! Read the last comment posted below, this information has been fixed in between – Huge Pages is definitively not possible with AMM !

Huge Pages were introduced in order to optimize the process of Memory Management on Linux Servers. The scope of this article is not to present in detail this technology, several articles and metalink note did this well (749851.1 – 361323.1 – 401749.1). Running Linux servers configured with Huge Pages was not always adapted when both 10.2 and 11.2 databases had to be started in parallel because the Oracle 11g Automatic Memory Management was not compatible with Huge Pages. This situation changed with Oracle!

As mentionned in Kevin Closson’s blog (see below), the release now supports Huge Pages and AMM (Automatic Memory Management) through the setting of the parameters memory_target and memory_max_size.


Moreover since it is possible to force the usage of Huge Page memory with the parameter use_large_pages=only.
When set to “only” this parameter prevents the instance to start on regular memory if not enough Huge Pages are available.

Per default the parameter is set to true, which means that if Huge Pages are available they will be used. If not enough Huge Pages are available Oracle will fall back to regular memory.

SQL>  show parameter use_large_pages
NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
use_large_pages                      string      TRUE

Since, while starting an Oracle instance, we have the following information in the alter.log file confirming that Huge Pages have been used.

Starting ORACLE instance (normal)
****************** Huge Pages Information *****************
Huge Pages memory pool detected (total: 25600 free: 24874)
DFLT Huge Pages allocation successful (allocated: 321)

The fact that Oracle supports Huge Pages and memory_target (which was not possible in the first 11g releases) confirms that Huge Pages are really advised by Oracle. So keep up to date and take care while reading metalink notes stating that “With AMM all SGA memory is allocated by creating files under /dev/shm. When Oracle DB does SGA allocations that way HugePages are not reserved/used. The use of AMM is absolutely incompatible with HugePages.” – ML note 749851.1

Through this improvement the configuration of Linux Servers running 10.2 and 11.2 in parallel becomes easier, since AMM is no more excluded.
Have fun with Huge Pages !