Oracle RAC on RedHat Linux Best Practice guide and ... - OpenMPE

<strong>Oracle</strong> VLM using shmfs or ramfs
• <strong>Oracle</strong> creates a “window” in its address space which it uses to
map/unmap various buffers from the SGA.
− The default size of this window is 512MB.
− The window size can be increased or decreased by setting the environment
variable VLM_WINDOW_SIZE to the size of the windows desired.
• The mapping/unmapping happens relatively quickly via memory
page table manipulation and does not result in memory copies.
• The non database buffer areas of the SGA must still fit under
the 2.7GB SGA limit.
• <strong>Oracle</strong> Total SGA Size – Database Buffers +
VLM_WINDOW_SIZE