ORA-00845: MEMORY_TARGET not supported on this system

Problem
In my 2-nodes 11.2.0.2 RAC database on OEL5.5 platform, after I uninstalled 10g database software, the "srvctl start database -d racdb" failed with following error message:

ORA-00845: MEMORY_TARGET not supported on this  system

Cause of the Problem

My google search lands me on this page, so I followed the instructions by issuing following commands:

df -h

*****

tmpfs                  32G   18G   14G  56% /dev/shm

*****

So in my 2-nodes RAC database, there is only 32G memory mounted on tmpfs, but the db was created with a MEMORY_TARGET=30144M

SQL> show parameters memory

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

hi_shared_memory_address             integer     0

memory_max_target                    big integer 30144M

memory_target                        big integer 30144M

shared_memory_address                integer     0

Solution

1 To temporarily fix this problem by increasing the mounted tmpfs size to 40G (run below command as root user)

 mount -t tmpfs shmfs -o size=40g /dev/shm

2 To permanently fix this problem, add following line to the /etc/fstab file as "root" user.  So next time when the server reboots, the mounted memory size will stay as 40 G.

shmfs /dev/shm tmpfs size=40g 0