ORA-27104: system-defined limits for shared memory was misconfigured

When i try to start the instance, i am getting below error.

ORA-27104: system-defined limits for shared memory was misconfigured


Solution:

In this case i have increased the kernel.shmmax to 75GB and SGA_TARGET is 50, after changes if i try to start the database getting below error.

SQL*Plus: Release 12.2.0.1.0 Production on Fri Jan 3 22:37:58 2020

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Connected to an idle instance.

SQL> startup pfile='/tmp/pfile.ora';
ORA-27104: system-defined limits for shared memory was misconfigured


Note: when ever you increase shmmax we should also increase kernel.shmall.

Now kernal values as below:

kernel.shmmni = 4096
kernel.shmall = 12261931
kernel.shmmax = 75161927680

but shmall value should be as below.

kernel.shmall =  kernel.shmmax/kernel.shmmni

as per my kernal values  75161927680/4096=18350080, but currently its 12261931, i changed kernel.shmall  to 18350080, issue resolved i am able to start the database.

kernel.shmall = 18350080

Hope this help.