ORA-27154 ORA-27300 ORA-27301 ORA-27302 from Instance Startup

Always make sure “kernel.sem = SEMMSL SEMMNS SEMOPM SEMMNI” set-up correctly to avoid issues.

The following errors occurred while starting up a 12.2.0.1 Oracle database instance.

SQL> startup

ORA-27154: post/wait create failed
ORA-27300: OS system dependent operation:semget failed with status: 28
ORA-27301: OS failure message: No space left on device
ORA-27302: failure occurred at: sskgpcreates

The error “operation:semget failed with status: 28” points out that it could be semaphore resource issue.

Oracle 12.2.0.1 doc recommended minimum value for semaphore are :

kernel.sem = SEMMSL SEMMNS SEMOPM SEMMNI
SEMMSL - max semaphores per array
SEMMNS - max semaphores system wide
SEMOPM - max ops per semop call
SEMMNI - max number of arrays

semmsl  =   250
semmns  = 32000
semopm  =   100
semmni  =   128

Check current system configuration for semaphores:

$ cat /proc/sys/kernel/sem
250 32000 100 200

$ ipcs -ls

------ Semaphore Limits --------
max semaphores per array   = 250
max semaphores system wide = 32000
max ops per semop call     = 100
max number of arrays       = 200
semaphore max value        = 32767

We can see SEMMNS is not right. it is supposed to be equal to SEMMSL*SEMMNI =250*200=50000.

If  SEMMNS  value too small, then we have to increase SEMMNI first, then adjust SEMMNS to SEMMSL*SEMMNI.

Set semaphore kernel parameter dynamically without the need for server reboot:

# sysctl -w kernel.sem="250 50000 100 200"
kernel.sem = 250 50000 100 200

-- Put into file
cat /etc/sysctl.conf | grep kernel.sem
kernel.sem = 250 50000 100 200

Or put into /etc/sysctl.conf file first, then

# sysctl -p

Then verify the current semaphore configurations:

# ipcs -ls

------ Semaphore Limits --------
max number of arrays       = 200
max semaphores per array   = 250
max semaphores system wide = 50000
max ops per semop call     = 100
semaphore max value        = 32767

Finally start up instance successfully.

SQL> startup
ORACLE instance started.

Total System Global Area 4294967296 bytes
Fixed Size 8801008 bytes
Variable Size 1073743120 bytes
Database Buffers 3187671040 bytes
Redo Buffers 24752128 bytes
Database mounted.
Database opened.

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