There is always something that gets in the way. One problem I regularly stumble upon when installing a new Oracle 11g R2 installation is the following error when I try to start the database:
SQL> startup nomount;
ORA-00845: MEMORY_TARGET not supported on this system
So I keep this post mainly for my own reference when installing a new database on a Linux system.
This error comes up because you tried to use the Automatic Memory Management (AMM) feature of Oracle 11g R2. Well done, but it seems that your shared memory filesystem (shmfs) is not big enough. So let’s look at the steps necessary to enlarge your shared memory filesystem to avoid the error above.
First of all, login as root and have a look at the filesystem:
[root@oracle-em oracle]# df -h
Filesystem Size Used Avail Use% Mounted on
93G 19G 69G 22% /
tmpfs 5.9G 112K 5.9G 1% /dev/shm
/dev/sda1 485M 99M 362M 22% /boot
So we can see that
tmpfs has a size of 6GB. We can change the size of that filesystem by issuing the following command (where “12g” is the size I want for my MEMORY_TARGET):
[root@oracle-em oracle]# mount -t tmpfs shmfs -o size=12g /dev/shm
This command (re)mounts the shmfs filesystem (check this post for more information about shmfs) with the option “
The shared memory file system should be big enough to accommodate the
MEMORY_MAX_TARGET values, or Oracle will throw the ORA-00845 error. Note that when changing something with the
mount command, the changes are not permanent.
To make the change persistent, edit your
/etc/fstab file to include the option you specified above:
[root@oracle-em ~]# 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 should 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
Database Buffers 5804916736 bytes
Redo Buffers 12128256 bytes
Bingo! Now go and enjoy your automatically managed memory configuration!