ORA-00845: MEMORY_TARGET not supported on this system

SQL> startup nomount;

This error occurs because you tried to use the automatic feature memory management (AMM) Oracle 11g R2. But it seems that its shared memory file system (shmfs) is not big enough. So let's look at the necessary steps to expand its shared memory file system to avoid the above error.

First of all, log in as root and check the file system:

[Root @ oracle in oracle] # df -h
 Filesystem Size Used Avail Use% Mounted on
 /Dev/mapper/vg_oracleem-lv_root
 93G 19G 69g 22% /
 tmpfs 112K 5.9G 5.9G 1% /dev/shm
 /Dev/sda1 99M 485M 362M 22% /boot

So we can see that tmpfs has a 6GB in size. We can change the file system size with the following command:

[Root @ oracle in oracle] # mount -t tmpfs -o shmfs size = 12g /dev/shm

This command (re) mounts the system shmfs files. The shared memory file system must be large enough to accommodate the MEMORY_TARGET and MEMORY_MAX_TARGET values, or Oracle will report ORA-00845 error. Note that when you change something with the mount command, the changes are not permanent.

To make the change persistent, edit your /etc/ fstab to include the option specified above:

[Root @ oracle-in ~] # cat /etc/fstab
 [..]
 tmpfs / dev / shm tmpfs size = 12g 0 0
 [..]

In my case, I replaced the "defaults" option with the size = 12g option. After saving the file, the changes must be permanent. Now back to Oracle. Let's see if we can start the database now ...

SQL> startup nomount
 ORACLE instance started

Total System Global Area 1.1758E + 10 bytes
 Fixed Size 2239056 bytes
 Variable Size 5939135920 bytes
 5804916736 bytes Database Buffers
 Redo Buffers 12128256 bytes

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