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242 - ORA-00845 When Starting Up An 11g Instance With AMM Configured

On a Linux system, trying to start up an 11g instance could fail with the following error :

ORA-00845: MEMORY_TARGET not supported on this system

Iin terms of 11g, MEMORY_TARGET is used instead of SGA_TARGET and MEMORY_MAX_TARGET is used instead of
Also please confirm that ORACLE_HOME is set correctly, this error sometimes happens when it's not set correctly.

It uses /dev/shm on Linux. If max_target set over /dev/shm size, you get the error messages ORA-00845 as well.

1. Size on /dev/shm

If you are installing Oracle 11g on a Linux system, note that Memory Size (SGA and PGA), which sets
the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, cannot be greater than
the shared memory filesystem (/dev/shm) on your operating system.
To resolve the current error, increase the /dev/shm file size. For example :

# mount -t tmpfs shmfs -o size=7g /dev/shm

Also, to make this change persistent across system restarts, add an entry
in /etc/fstab similar to the following :

shmfs /dev/shm tmpfs size=7g 0

2. The error may also occur if /dev/shm is not properly mounted.

Make sure your df output is similar to the following :

$ df -k
Filesystem 1K-blocks Used Available Use% Mounted on
shmfs 6291456 832356 5459100 14% /dev/shm

3. If configuring AMM is not possible due to lack of space on /dev/shm mount point, you can configure ASMM instead of AMM.


Note: In Linux, /dev/shm is needed only for AMM. ASMM uses regular shared segments instead,
so /dev/shm would not need any change at all.




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