ORA-00845: MEMORY_TARGET not supported on this system

In my testing environment on virtual box, after upgrading standalone Grid+ASM from 11.2.0.4 to 12.1.0.2 on Oracle Linux 6.5. i have experienced "MEMORY_TARGET not supported" error when i tried to connect to ASM instance.

Causes of the Problem are listed below.
1. Since Oracle 11g introduced Automatic Memory Management new features defined with MEMORY_TARGET and MEMORY_MAX_TARGET parameters to manage the SGA and PGA together.

2. On Linux file system the shared memory should be mounted on /dev/shm directory.

3. The size of the /dev/shm should be greater than the MEMORY_TARGET and MEMORY_MAX_TARGET.

4.  Error "ORA-00845: MEMORY_TARGET not supported on this system" rises due to less size of the shared memory  mapped to  /dev/shm directory or shared memory is not mapped.

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

Check the shared memory size.

[root@oracle123 ~]# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        39G  8.9G   28G  25% /
tmpfs           1.1G   72K  1.1G   1% /dev/shm
/dev/sda3       4.7G   22M  4.5G   1% /tmp
/dev/sda1        48G  9.1G   37G  20% /u01
/dev/sda6        53G  6.8G   43G  14% /u02

Allocate sufficient size for the shared memory. 

[root@oracle123 ~]# mount -t tmpfs shmfs -o size=4g /dev/shm

To make permanent add into the fstab.

[root@oracle123 ~]# vi /etc/fstab 
[oracle@oracle123 ~]$ cat /etc/fstab 

#
# /etc/fstab
# Created by anaconda on Sat Mar 19 10:40:01 2016
#
# Accessible filesystems, by reference, are maintained under '/dev/disk'
# See man pages fstab(5), findfs(8), mount(8) and/or blkid(8) for more info
#
UUID=69ab4b0e-0dd2-41e6-86ae-8e6573b6754e /                       ext4    defaults        1 1
UUID=3435f7a7-6f44-4e9e-a0c8-1ca4d83ad963 /tmp                    ext4    defaults        1 2
UUID=7c1f5871-8862-4431-ac80-6740311c2201 /u01                    ext4    defaults        1 2
UUID=1f9c80c3-6007-4f90-93e1-9e994a68fd95 /u02                    ext4    defaults        1 2
UUID=2c626767-596b-405d-9599-ad95a17b0538 swap                    swap    defaults        0 0
tmpfs                   /dev/shm                tmpfs   size=4g        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0

Verify again.

[oracle@oracle123 ~]$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        39G  8.9G   28G  25% /
tmpfs           4.0G  862M  3.2G  22% /dev/shm
/dev/sda3       4.7G   22M  4.5G   1% /tmp
/dev/sda1        48G  9.1G   37G  20% /u01
/dev/sda6        53G  6.9G   43G  14% /u02

Once shared memory mounted and sufficient size allocated. we can connect to the instance without error.

Thanks.