SQL> startup nomount; ORA-00845: MEMORY_TARGET not supported on this system
This error comes up because we tried to use the Automatic Memory Management (AMM) feature of Oracle 11g R2. But it seems that your shared memory filesystem (shmfs) is not big enough.
[oracle@oel6 ~]$ df -h Filesystem Size Used Avail Use% Mounted on /dev/mapper/vg_oel6-lv_root 43G 15G 26G 37% / tmpfs 1001M 212M 789M 22% /dev/shm /dev/sda1 485M 55M 405M 12% /boot .host:/ 245G 126G 119G 52% /mnt/hgfs
We can change the size of that filesystem by issuing the following command:
mount -t tmpfs shmfs -o size=2g /dev/shm
The shared memory file system should be big enough to accommodate the MEMORY_TARGET and MEMORY_MAX_TARGET values, or Oracle will throw the ORA-00845 error. Note that when changing something with the mount command, the changes are not permanent.
To make the change persistent, edit your /etc/fstab file
tmpfs /dev/shm tmpfs defaults,size=2G 0 0
Now go and enjoy your automatically managed memory configuration!