This note apply to Oracle Database 11g and linux S.O.
On a Linux system, trying to start up an 11g instance could fail with the following error:
ORA-845: MEMORY_TARGET not supported on this system
In the alert log, you could or could not see the below messages:
The problem occur when use AMM (Automatic Memory Management) and the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, is greater than the shared memory filesystem (/dev/shm) on your operating system.
Mount filesystem (/dev/shm) :
mount -t tmpfs shmfs -o size=16g /dev/shm
Add in (/etc/fstab) :
tmpfs /dev/shm tmpfs defaults 0 0
See the filesystem :
tmpfs 16G 13G 2.9G 82% /dev/shm
Good Luck !