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is AMM now compatible with huge pages?
No - but Automatic Shared Memory Management and Automatic PGA Management are.
See the Database Administrator's Reference
11g Release 2 (11.2) for Linux and UNIX-Based Operating Systems
G.2.3 Restrictions for HugePages Configurations
Following are the limitations of using HugePages:
•The Automatic Memory Management (AMM) and HugePages are not compatible. With AMM the entire SGA memory is allocated by creating files under /dev/shm. When Oracle Database allocates SGA that way HugePages are not reserved. You must disable AMM on Oracle Database to use HugePages.
•If you are using VLM in a 32-bit environment, then you cannot use HugePages for the Database Buffer cache. HugePages can be used for other parts of SGA like shared_pool, large_pool, and so on. Memory allocation for VLM (buffer cache) is done using shared memory file systems (ramfs/tmpfs/shmfs). HugePages does not get reserved or used by the memory file systems.
•HugePages are not subject to allocation or release after system startup, unless a system administrator changes the HugePages configuration by modifying the number of pages available, or the pool size. If the space required is not reserved in memory during system startup, then HugePages allocation fails.
sb92075 wrote:Why do you waste your time here then continually criticizing posters and ignoring their problems?
Status Level: Newbie
Registered: Apr 14, 2010
Total Posts: 17
Total Questions: 5 (5 unresolved)
why do you waste time here when you never get answers to any of your questions?
Kernel Hugepages and Posix shared memory are not compatible and mutually exclusive. The benefit of Hugepages stems from a larger page allocation size and guarantee that this memory, unlike Posix shared memory, will not be swapped to disk. Hugepages are reserved at system startup. From what I understand, you will still have to configure your Database startup parameter to either use AMM (/dev/shm) or ASMM to use kernel hugepages. The change introduces a fail-over to utilize additional regular memory for Oracle SGA in case the amount of available Hugepages is insufficient.