ORA-00845: MEMORY_TARGET not supported on this system

Hi DBA-Mates,
Sometimes when we all try to connect 11g (newly installed software) and then trying to STARTUP the database, we faced below error message as shown below:

$ sqlplus ‘/as sysdba’
SQL*Plus: Release 10.1.0.5.0 - Production on Mon Nov 21 16:12:11 2016
Copyright (c) 1982, 2005, Oracle.  All rights reserved.
Connected to:

Oracle Database 11g Enterprise Edition Release 11.2.0.4.0 - 64bit Production with the Partitioning, Automatic Storage Management, OLAP, Data Mining and Real Application Testing options

SQL> STARTUP

ORA-00845: MEMORY_TARGET not supported on this system

Solution:
1.  Suppose, we are installing Oracle database 11g on a Linux operating system, it should be noted that Memory Size like SGA and PGA, which sets the initialization parameter MEMORY_TARGET or MEMORY_MAX_TARGET, should not be greater than the shared memory file system (/dev/shm) on your operating system.

2.  So, to resolve this above error, we should increase the /dev/shm file system size.

3. Login as root user.

$su – root
Password: *****

# mount -t tmpfs shmfs -o size=5g /dev/shm

After that again start your database.
$sqlplus / as sysdba

SQL> startup

database open.

SQL>

Explanation: 

Actually, the file system /dev/shm should to be mounted. It should be automatically available but sometimes it might be missed during installation.
And if /dev/shm is mounted, but still facing issue then might be it has mounted with available space less size, which can be avoid by mounting and resizing the mount point.

As, we all know the new feature of 11g in which one of them is AMM. (Automatic Memory Management) which manages both SGA and PGA.

We all knowing the database concept where database parameter MEMORY_TARGET is used instead of SGA_TARGET and 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 get the error messages.

Also, this error may also occur if /dev/shm is not properly mounted. We can check this by using df command as shown below:

$ df -k 

Filesystem 1K-blocks Used Available Use% Mounted on
shmfs 6291455 832355 5458 99 13% /dev/shm

I have modified the above df -k output. Above output should be similar to that.

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Hope this information useful and helpful for you all. For any concerns or suggestions, please let us know either in comment box or contact us at our blog ora-data.blogspot.com.

Thanks,