ORA-00845: MEMORY_TARGET not supported on this system

WARNING: You are trying to use the MEMORY_TARGET feature. This feature requires the /dev/shm file system to be mounted for at least 314572800 bytes. /dev/shm is either not mounted or is mounted with available space less than this size. Please fix this so that MEMORY_TARGET can work as expected. Current available is 15183872 and used is 161312768 bytes. Ensure that the mount point is /dev/shm for this directory.
memory_target needs larger /dev/shm

[root@ygzhou518 ~]# mount -t tmpfs shmfs -o size=1500m /dev/shm