[ORA-00845: MEMORY_TARGET not supported on this system] is a very common error message you will get when you try to install Oracle 11gR1 or Oracle 11gR2 on Unix platforms. I had encountered this while installing Oracle 11gR1 on Suse Linux 10.
To install Oracle go to $ORACLE_HOME/bin and then do a ./runInstaller at the prompt. Make sure you run it with oracle user and not root user.
It open up the installation GUI. During the end part of installation, it will configure the database. The screen looks something like Fig1.
You are most likely to get the error popup during this configuration check.
You may also get a similar error while starting the database at the SQL prompt.
ORA-00845: MEMORY_TARGET not supported on this system
Make sure that /dev/shm is mounted. You can check this by typing df -k at the command prompt. It will look something
Filesystem Size Used Avail Use% Mounted on
shmfs 1G 512M 512M 50% /dev/shm
If you don't find it then you will have to manually mount it as root user. The size should be more than MEMORY_TARGET or MEMORY_MAX_TARGET. For example the MEMORY_TARGET is less than 2 GB.
# mount -t tmpfs shmfs -o size=2048m /dev/shm
You should add an entry in /etc/fstab so that the mount remains persistent even after a reboot. Add the following entry in /etc/fstab.
shmfs /dev/shm tmpfs size=2048m 0 0