The software described in this documentation is either in Extended Support or Sustaining Support. See https://www.oracle.com/us/support/library/enterprise-linux-support-policies-069172.pdf for more information.
Oracle recommends that you upgrade the software described by this documentation as soon as possible.
Oracle Linux releases prior to Oracle Linux 5 supplied a
hugemem kernel to allow a system to address
up to 64 GB of memory in 32-bit mode. The
hugemem kernel is no longer available in
Oracle Linux 5 and later releases.
UEK supports a maximum of 16 GB of memory for 32-bit kernels on bare metal and HVM systems, and 8 GB for fully PVM systems. Note that 32-bit PVM guest operating systems must be located in the first 128 GB of physical memory on the host.
RHCK has the same limitations, except that PVM systems can have up to 16 GB of memory. The 8 GB limitation for PVM on UEK was chosen for reasons of reliability.
A 32-bit system uses the PAE (physical address extension) memory feature to map physical memory beyond 4 GB into the 32-bit address space that is available to each process. A 64-bit system can address memory beyond 4 GB without requiring an extra layer of memory abstraction.
Oracle Linux on x86-64 includes 32-bit libraries, which allow applications that are built for both 64-bit and 32-bit Linux to run on the same system. This capability provides scalability to virtually unlimited memory sizes, while retaining the ability to run 32-bit applications. Oracle recommends this configuration for any system with more than 4 GB of memory. (Bug ID 16974301)