Home > Uncategorized > ORA-00845: MEMORY_TARGET not supported on this system

ORA-00845: MEMORY_TARGET not supported on this system

Example taken from http://arjudba.blogspot.com/2009/01/ora-00845-memorytarget-not-supported-on.html

SQL> STARTUP
ORA-00845: MEMORY_TARGET not supported on this system

Cause of the Problem
•Starting from Oracle 11g the automatic memory management feature is now defined with parameter MEMORY_TARGET and MEMMORY_MAX_TARGET.

•On linux file system the shared memory need to be mounted on /dev/shm directory on the operating system.

•And the size of /dev/shm needs to be greater than MEMORY_TARGET or MEMMORY_MAX_TARGET.

•The AMM (Automatic Memory Management) now in 11g manages both SGA and PGA together by MMAN process.

•The MEMORY_TARGET parameter in 11g comes for (SGA_TARGET+PGA_AGGREGATE_TARGET) which was in 10g.

•And MEMORY_MAX_TARGET parameter in 11g comes instead of SGA_MAX_TARGET parameter which was in 10g.

•The ORA-00845:can arises for the following two reasons on linux system.

1)If the shared memory which is mapped to /dev/shm directory is less than the size of MEMORY_TARGET or MEMORY_MAX_TARGET.
or,
2)If the shared memory is not mapped to /dev/shm directory.

Solution of the Problem

Make sure /dev/shm is properly mounted. You can see it by,
df -h
The output should be similar like
$ df -kFilesystem            Size  Used Avail Use% Mounted on…shmfs                 1G    512M 512M  50% /dev/shm

We see here for /dev/shm we have assigned 1G memory. Now if you set MEMORY_TARGET more than 1G then above ORA-845 will arise. For example if you have MEMORY_TARGET or MEMORY_MAX_TARGET set to 12G then you can mount shared memory to 13g like below.

As a root user,
# mount -t tmpfs shmfs -o size=13g /dev/shm

In order to make the settings persistence so that it will affect after restarting machine add an entry in /etc/fstab similar to the following:

shmfs /dev/shm tmpfs size=13g 0

Advertisements
Categories: Uncategorized
  1. No comments yet.
  1. No trackbacks yet.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s

%d bloggers like this: