ORA-00845: MEMORY_TARGET not supported on this system

A known issue, when starting database.

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

This is due to low space on tmpfs (/dev/shm)

[oracle@node1 ~]$ df -h

Filesystem            Size  Used Avail Use% Mounted on

tmpfs                1006M  520M  486M  52% /dev/shm

[root@node1 +ASM]#  mount -o remount,size=3G /dev/shm

[root@node1 +ASM]# df -h

Filesystem            Size  Used Avail Use% Mounted on

tmpfs                 3.0G  520M  2.5G  17% /dev/shm

[root@node1 +ASM]# vi /etc/fstab

Update fstab file with size=<size> for tmpfs

tmpfs                   /dev/shm                tmpfs   defaults,size=3G       0 0

[root@node1 +ASM]# mount -a

[root@node1 +ASM]# df -h

Filesystem            Size  Used Avail Use% Mounted on

tmpfs                 3.0G  520M  2.5G  17% /dev/shm

Start the database and it starts normally.