ORA-27102: out of memory on Linux, unable to startup instance

Lower value of “kernel.shmall” in /etc/sysctl.conf will result “ORA—27102: out of memory” error on Linux x86_64,
set the value using below Formula. kernel.shmall = kernel.shmmax/PAGE_SIZE
Run the below command to get the value of PAGE_SIZE.
$getconf PAGE_SIZE
The kernel.shmmax parameter should be greater than or equal to the Half the size of physical memory (recommended value) of the machine.
If the amount of Physical memory is ever changed then the parameter should be adjusted accordingly.

To make the new kernel settings take effect immediately, run this command:

$/sbin/sysctl -p