Recently a customer observed on one of their systems, that the number n of databases started quite nicely on a system. However when they tried to start database n+1 on it, it just yielded the following error message.
SQL> startup
ORA-27125: unable to create shared memory segment
SVR4 Error: 28: No space left on deviceYour first reflex ist to check the amount of free shared memory, but the system had ample of it free. My first reflex after seeing an unlimited ZFS ARC was that we simply run out of memory and that the customer should limit that at first. However then i remembered there is a second resource that creates this errormessage as well. It’s the number of shared memory IDs. You have to check them as well. Per default they are limited to 128.
$ prctl -n project.max-shm-ids -i process $$
process: 4457: -ksh
NAME PRIVILEGE VALUE FLAG ACTION RECIPIENT
project.max-shm-ids
privileged 128 - deny -
system 16.8M max deny I suggested to increase this number significantly.
# projmod -A -s -K "project.max-shm-ids=(privileged,1024,deny)" user.oracleLet’s check the situation again.
$ prctl -n project.max-shm-ids -i process $$
process: 16382: -ksh
NAME PRIVILEGE VALUE FLAG ACTION RECIPIENT
project.max-shm-ids
privileged 1.02K - deny -
system 16.8M max deny After this, the database n+1 started without any problem.
