How to resolve ora-00845 ?

SQL> startup;
ORA-00845: MEMORY_TARGET not supported on this system
SQL> !df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/mapper/vg_bodb-lv_root
                       26G   14G   12G  55% /
tmpfs                 5.7G   72K  5.7G   1% /dev/shm  <-- increase size of tmpfs
/dev/xvda1            477M   72M  376M  17% /boot
/dev/mapper/BODB_ORADATA-ORADATA
                      688G   12G  642G   2% /oradata
/dev/mapper/BODB_FRA-BODB_FRA
                       98G   75M   93G   1% /orafra

vi /etc/fstab
existing line :-
tmpfs                   /dev/shm                tmpfs   defaults        0 0
new line :-
tmpfs                   /dev/shm                tmpfs   size=8G        0 0