Dotaz (Question)

hi tom ... how are you

can you help me please

I have this message with my oracle 11g database

ORA-00845: MEMORY_TARGET not supported on this system

could you please tell me the best setting for my SHARED MEMORY

oracle@mohammad-laptop:~$ df -k
Filesystem           1K-blocks      Used Available Use% Mounted on
/dev/sda5            238441596  46148208 180181184  21% /
tmpfs                   516124         0    516124   0% /lib/init/rw
varrun                  516124       108    516016   1% /var/run
varlock                 516124         0    516124   0% /var/lock
udev                    516124      2820    513304   1% /dev
tmpfs                   516124    270652    245472  53% /dev/shm
lrm                     516124      2204    513920   1% /lib/modules/2.6.27-17-generic/volatile
/dev/sda1               671968     41124    596708   7% /boot

Odpověd (Answer)

Hello Mohammad,

this is part of metalink note
ORA-00845: MEMORY_TARGET not supported on this system - Linux Servers [ID 465048.1]

Cause

On Linux systems, insufficient /dev/shm mount size for PGA and SGA.

AMM (Automatic Memory Management) is a New feature in 11G which manages both SGA and PGA
together. Its is managed by MMAN, same as with 10g AMM

MEMORY_TARGET is used instead of SGA_TARGET
MEMORY_MAX_TARGET is used instead of SGA_MAX_SIZE (defaults to MEMORY_TARGET )

It uses /dev/shm on Linux

If max_target set over /dev/shm size, you may  get the below error message ::

ORA-00845: MEMORY_TARGET not supported on this system

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.

NOTE:

This 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

Solution

Increase the /dev/shm mountpoint 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

NOTE:  You should check with your OS Administrator and/or alert.log for information on "best" size fo shm.