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I had installed Oracle 12 to my Linux box. I tried to login using sqlplus but it prompt out this error at below. How to solve it?
Enter user-name: SYSDBA
Enter password: ERROR: ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3701
Additional information: 542678011
Process ID: 0 Session ID: 0 Serial number: 0
EDIT: How to find out default ORACLE_SID?
There could be various reason for this error.
ORACLE_SID and ORACLE_HOME.
When you have wrong ORACLE SID and HOME.
I could reproduce the error by changing my SID to something else. My SID is oracdb.
[oracle@myserver ~]$ ps -ef | grep pmon
oracle 29336 1 0 Apr27 ? 00:00:22 ora_pmon_oracdb
But I changed it to orcl.
[oracle@myserver Desktop]$ export ORACLE_SID=orcl
Then I tried to connect to the database using SQL*PLUS.
[oracle@myserver Desktop]$ sqlplus sys
SQL*Plus: Release 12.2.0.1.0 Production on Tue May 2 00:23:50 2017
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Enter password:
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3701
Additional information: -923528497
Process ID: 0
Session ID: 0 Serial number: 0
Then I changed it to original SID.
[oracle@myserver ~]$ export ORACLE_SID=oracdb
[oracle@myserver ~]$ sqlplus / as sysdba
SQL*Plus: Release 12.2.0.1.0 Production on Tue May 2 00:28:40 2017
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
When your instance is down and connected as a non-sys user
Use the following linux command to check whether some of the important background processes are running or not such PMON or SMON.
[oracle@myserver ~]$ ps -ef| grep pmon
oracle 57587 57044 2 00:52 pts/3 00:00:00 grep pmon
My oracle instance is down.
Now, as you have tried, I attempt to connect to the database using non-sys user, sysdba is a privilege not a database user.
[oracle@myserver ~]$ sqlplus sysdba
SQL*Plus: Release 12.2.0.1.0 Production on Tue May 2 00:53:04 2017
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Enter password:
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Additional information: 3701
Additional information: -688980181
Process ID: 0
Session ID: 0 Serial number: 0
Enter user-name:
I got the same error as you have got.
Now, connect as sysdba/sysoper and start the database instance.
[oracle@myserver ~]$ sqlplus / as sysdba
SQL*Plus: Release 12.2.0.1.0 Production on Tue May 2 00:53:36 2017
Copyright (c) 1982, 2016, Oracle. All rights reserved.
Connected to an idle instance.
SQL> startup
$ORACLE_HOME/dbs directory and find initialization parameter files such as spfile<SID>.ora or init<SID>.ora.
$ ps -ef | grep pmon shows instance name at the end of the process name.