ORA-27125: unable to create shared memory segment Linux-x86_64 Error: 28: No space left on device

When starting up an Oracle database, the below errors occur:

ORA-27125: unable to create shared memory segment
Linux-x86_64 Error: 28: No space left on device
Additional information: 3773
Additional information: 3221225472

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Reconfigure OS Parameters After Linux Server Memory Upgrade

Adjust OS memory parameters after more or less memory available

One of the Oracle database server ‘s memory is to be upgraded from 48GB to 72GB, so some parameters should be adjusted to take advantage of the newly added memory.

Change memlock Parameter

Modify “memlock” parameter in /etc/security/limits.conf to 70G, which is for hugepage purpose. This parameter can be bigger than SGA, up to or even bigger than memory size.

oracle  soft      memlock  73400320
oracle  hard      memlock  73400320
  grid  soft      memlock  73400320
  grid  hard      memlock  73400320

Change nr_hugepages Parameter

Change parameter ‘nr_hugepages’  in /etc/sysctl.conf.
43GB memory( 60% of whole memory ) is allocated to hugepages.

vm.nr_hugepages = 22016

Change shmmni, shmall and shmmax  values in /etc/sysctl.conf

 a)Keep kernel.shmmni = 4096

b) kernel.shmall=13369344 (51GB)  = 70% of whole memory divided by page size 4096.

c ) kernel.shmmax=38654705664( 36GB) =  50% of the whole memory size.

kernel.shmmni = 4096
kernel.shmall = 13369344
kernel.shmmax = 38654705664

Reconfigure SGA_TARGET and SGA_MAX_SIZE

Make sure the total SGA usage is less than vm.nr_hugepages = 22016( 43GB).