solve ORA-00845: MEMORY_TARGET not supported on this system

I recently tried to start an "old" Oracle 11G database which was installed on a system I used for some other projects. Due to the other projects some settings to the operating system have changed.

When the database was started during the system boot I found an error on the console stating the following error:

ORA-00845: MEMORY_TARGET not supported on this system

It turned out that my tmpfs filesystem was to small for the original settings of my Oracle database. tmpfs is a common name for a temporary file storage facility on many Unix-like operating systems. It is intended to appear as a mounted file system, but stored in volatile memory instead of a persistent storage device. A similar construction is a RAM disk, which appears as a virtual disk drive and hosts a disk file system.

You can check your tmpfs mount with a simple df -h command like below (this is the state after the change):

[oracle@oem bin]$ df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/xvda2            4.1G  3.0G  1.1G  75% /
/dev/xvda1             92M   12M   76M  14% /boot
tmpfs                 3.0G  1.2G  1.8G  41% /dev/shm
/dev/xvdb1             27G   13G   13G  49% /u01
[oracle@oem bin]$

It turned out the size was not 3.0G and it turned out that my database settings where set for a 2.0G system. You can check this by executing the following command's"

SQL>
SQL> show parameter MEMORY_MAX_TARGET;

NAME                     TYPE     VALUE
------------------------------------ ----------- ------------------------------
memory_max_target             big integer 2G
SQL> show PARAMETER MEMORY_TARGET;

NAME                     TYPE     VALUE
------------------------------------ ----------- ------------------------------
memory_target                 big integer 2G
SQL>
SQL>

This shows we need at least 2.0G, to be sure I made my tmpfs 3.0G by editing my /etc/fstab file. Originally it looked like the one below:

[oracle@oem bin]$ cat /etc/fstab
LABEL=/                 /                       ext3    defaults        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-VM           swap                    swap    defaults        0 0
LABEL=oms               /u01                    ext3    defaults        1 2
[oracle@oem bin]$

You can change it to the example below so you will mount 3.0G:

[oracle@oem bin]$ cat /etc/fstab
LABEL=/                 /                       ext3    defaults        1 1
LABEL=/boot             /boot                   ext3    defaults        1 2
tmpfs                   /dev/shm                tmpfs   size=3000m        0 0
devpts                  /dev/pts                devpts  gid=5,mode=620  0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-VM           swap                    swap    defaults        0 0
LABEL=oms               /u01                    ext3    defaults        1 2
[oracle@oem bin]$