If you get this type of error while starting up database using startup command

SQL> startup nomount;
ORA-00845: MEMORY_TARGET not supported on this system


Solution:

Increase tmpfs mount on filesystem to some extent still you overcome MEMORY_TARGET error


mount -t tmpfs shmfs -o size=12g /dev/shm


If you need it permanantly edit "/etc/fstab" and make changes like below

tmpfs                   /dev/shm                tmpfs   size=12g        0 0


Note:

Replace the “defaults” option with the size=12g option.



After saving the file, the changes should be permanent. Now back to Oracle. Let’s see if we can start the database now..