ORA-01034: ORACLE not available in oracle 11g

Question

I installed oracle 11g on ubuntu 14.04 and i started lister and the message is as below.

LSNRCTL for Linux: Version 11.2.0.2.0 - Production on 10-OCT-2014 14:20:02
Copyright (c) 1991, 2011, Oracle. All rights reserved.
Starting /u01/app/oracle/product/11.2.0/xe/bin/tnslsnr: please wait...
TNSLSNR for Linux: Version 11.2.0.2.0 - Production
System parameter file is /u01/app/oracle/product/11.2.0/xe/network/admin/listener.ora
Log messages written to /u01/app/oracle/diag/tnslsnr/TSDC/listener/alert/log.xml
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC_FOR_XE)))
Listening on: (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=TSDC)(PORT=1521)))
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC_FOR_XE)))
STATUS of the LISTENER
------------------------
Alias LISTENER
Version TNSLSNR for Linux: Version 11.2.0.2.0 - Production
Start Date 10-OCT-2014 14:20:02
Uptime 0 days 0 hr. 0 min. 0 sec
Trace Level off
Security ON: Local OS Authentication
SNMP OFF
Default Service XE
Listener Parameter File /u01/app/oracle/product/11.2.0/xe/network/admin/listener.ora
Listener Log File /u01/app/oracle/diag/tnslsnr/TSDC/listener/alert/log.xml
Listening Endpoints Summary...
 (DESCRIPTION=(ADDRESS=(PROTOCOL=ipc)(KEY=EXTPROC_FOR_XE)))
 (DESCRIPTION=(ADDRESS=(PROTOCOL=tcp)(HOST=TSDC)(PORT=1521)))
Services Summary...
Service "XE" has 1 instance(s).
 Instance "XE", status UNKNOWN, has 1 handler(s) for this service...
The command completed successfully

Then I started the server by oracle-xe start and it was started successfully.

When I was trying to connect to sql*plus following error was getting..

ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
Process ID: 0
Session ID: 0 Serial number: 0

Please suggest me what to do with this?

• sjk: Can you post the contents of listener.ora, $ORACLE_HOME and $ORACLE_SID? One possible cause for this error would be a trailing '/' after ORACLE_HOME in listener.ora
• captjackvane: please do a "ps -ef|grep pmon" on your server, and make sure the database you're looking for has an active PMON process. The error you have suggests that your DB is not running.
• mutap: sqlplus / as sysdba then issue command startup; to start the database.
• K M Dilshan Udara: i could't find the error.Finally i reinstalled oracle to solve the problem.
• Marko Bonaci: @mutap can you please write your comment in the form of an answer so I can +1. I searched for a whole day and couldn't find solution. Until I read your comment. Thanks

Answer 1

Run sqlplus / as sysdba then issue command startup; to start the database.

Also on Linux with this error, you can check first if Oracle background processes are up with ps aux | grep pmon. Pmon is process monitor, or check some other background process. If they are not running then the database is not running.