Tuesday, April 30, 2019

ORA-27125: unable to create shared memory segment during startup

Problem

After reboot, unable to startup Oracle 12c database instance (Red Hat Enterprise Server 7.6)

ORA-27125: unable to create shared memory segment
Linux-x86_64 Error: 28: No space left on device
Additional information: 3822
Additional information: 6157238272

Solution

Verify OS kernel.shmall memory setting.

1. Get current value 
cat /proc/sys/kernel/shmall
1677722

This seems to be too high..

2. Determine page size
getconf PAGE_SIZE
4096

3. Calculate recommended value for shmall

shmall = <total size of SGA>/<page size>

In our case, we have 16GB RAM, so, shmall = 16 * 1024 * 1024 * 1024 / 4096 = 4194304

4. Update /etc/sysctl.conf
vi /etc/sysctl.conf
kernel.shmall=4194304
sudo sysctl -p

5. Verify  kernel.shmall again
cat /proc/sys/kernel/shmall
4194304

6. Start Oracle instance
sudo su - oracle
sqlplus / as sysdba
startup;

This of course leads to another error..


References


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