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And here is what Oracle have to say about large pages:

The AIX operating system allows shared memory to be allocated in pinned memory for improved performance. Pinned memory is always present in real memory; it is not paged in and out. The primary advantage of using pinned memory for the Oracle System Global Area (SGA) is that I/O from pinned memory is optimized for improved path length.

This is possible because the asynchronous I/O routines do not need to pin the SGA memory each time it is used for an I/O operation. Because of this performance improvement, it is best to use pinned memory to allocate the Oracle SGA.

When the Oracle initialization parameter LOCK_SGA is set to TRUE, Oracle will allocate shared memory for the SGA using the AIX pinned memory. (Note: shmget() is called with the SHM_PIN flag set.) In addition to setting the Oracle LOCK_SGA parameter to TRUE, the AIX operating system must be configured to allow pinned memory to be used for shared memory.