Thursday, October 25, 2012

Linux HugPages With SGA

Normally when your Linux OS (no matter 32bit or 64bit)has more than 16G RAM while DB SGA is more than 8G, we recommend to set hugpages for SGA.
Just remember we can't use  Automatic Memory Management (AMM) and HugePages together.
The main benefit is to avoid swap in OS and save the PIN RAM,thus overall memory performance improves

The calculation is simple:

# Hugepages/bigpages values are strongly tied to SGA size.
#  vm.nr_hugepages = ((1+3%)*SGA_SIZE)/2MB

# vm.hugetlb_shm_group  = <oracle process group id>
# vm.hugetlb_shm_group  =1001

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