ORA-27125 When attempting to start 12c Database On Solaris 11

Issue: When attempting to start the 12c Database on Solaris 11, we hit the below error.

ORA-27125: unable to create shared memory segment
Invalid Argument.

Cause: The issue was due to an undersized project.max-shm-memory setting, where project.max-shm-memory was set to 8 GB while the RAM was 200 GB.

Solution:

Increase project.shm-max-memory to a value greater than 1/4 of physical memory.

The project.max-shm-memory resource control limits the total amount of shared memory of one project.
The PROJECT.MAX-SHM-MEMORY should be set larger than the sum of all segments used by the project.

In case, we don't set project.shm-max-memory but shmmax is defined, system assumes "shm-max-memory" as shmmax*shmmni. If shmmax is undefined as well,
then default value is 1/4 of physical memory:

 http://docs.oracle.com/cd/E19082-01/819-2724/6n50b0793/index.html


For example, to change the setting for project.max-shm-memory to 10 GB for the project default you can use either the 'prctl' command or the 'projmod' command. Changes made with the 'prctl' command are good only until system reboot. The 'projmod' command should be used to make changes that persist across reboot.

The following command requires reboot:

projmod -sK "project.max-shm-memory=(privileged,10G,deny)" user.dba

OR

To modify a parameter until next system reboot:

prctl -n project.max-shm-memory -v 6gb -r -i project user.dba