ORA-00845 Memory_target not supported

Error occurred when tried to start the database

sql>startup
ORA-00845 Memory Target not supported on this system

Reason:
System is out of temporary storage while starting the database oracle use /dev/shm for temporary storage if its out of space then above error occurred.

Solution
1. Check the df -h file system command to check the space allocated to /dev/shm

root@localhost# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 200G 15G  185G  61%  /
tmpfs     504M 76K  504M  1%   /dev/shm

2. For Oracle, /dev/shm file system on the nodes larger enough to support the AMM feature. So you need to increase the size of /dev/shm

On Linux: allocate large size
root@localhost# mount -o remount,size=3G /dev/shm

3. To make the change persistent on reboot add  following entries in the

/etc/fstab
root@localhost# vi /etc/fstab
tmpfs /dev/shm tmpfs defaults,size=3G 0 0

4. Verify the size of tmfs size again run df -h

root@localhost# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sda1 200G 15G  185G  61%  /
tmpfs     3g   76K  2.9G  1%   /dev/shm