ORA-27100: shared memory realm already exists tips
Oracle Error Tips by Stephanie F.
The Oracle docs note this on the
ORA-27100: shared memory realm
Cause: Tried to
start duplicate instances, or tried to restart an instance
that had not been properly shutdown
Action: Use a
different instance name, or cleanup the failed instance"s
Also see Startup Fails With ORA-27100 After Restarting The
Windows Service [MOSC ID 370469.1]
Typically, ORA-27100 can
be resolved by simply restarting Windows. However, Internet sources offer advice for times when this error is thrown, and not easily
resolved, applying to Oracle Enterprise; version 18.104.22.168.0 and Microsoft Server
2003. The error may be thrown similarly to the example below upon starting
up the database:
ORA-27100: shared memory realm already exists
SQL> shutdown immediate
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Restarted the service , still the same error.
Rebooting the server did not help as well.
This is caused by
- The parameter
sga_max_size was changed from 2GB to 3GB through OEM.
- Changing the parameter from OEM will make the change in the
- ORA-27100 is received as a result of changes made to parameters affecting
the SGA size.
- The service was created to start with
- When the service is restarted , it will use the
spfile and the error
occurs due to SGA parameter change.
To resolve ORA-27100,
you should execute the following instructions:
- Move the spfile
from its default location or rename the spfile .
Restart the service
Now the service will start the database using pfile , with old SGA
This should start your database successfully .
Create the new spfile from pfile.