Solved – How to troubleshoot ORA-01034: ORACLE not available issue?

What is the cause of the error “ORA-01034: ORACLE not available” when I log into sqlplus?

I got the following 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


The oerr Oracle utility shows this for the ORA-01034 error.

    Oracle was not started up. Possible causes include the following
    – The SGA requires more space than was allocated for it.
    – The operating-system variable pointing to the instance is improperly defined.

The Oracle instance that you are trying to connect to is not up and running.

Also ensure that the ORACLE_SID in the environment is correct and is the same as the instance you are trying to connect to.

In the example below the instance vst1 is not running on the host.

[[email protected] ~]$ echo $ORACLE_SID
[[email protected] ~]$ ps -ef|grep smon|grep $ORACLE_SID|grep -v ps

The only instance running on the host is cdb1.

[[email protected] ~]$ ps -ef|grep smon
oracle 2413 1 0 03:42 ? 00:00:04 ora_smon_cdb1

So start up the database after exporting the correct ORACLE_SID in the environment. Then you should be able to connect without the error being returned.

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Note: This Oracle documentation was created for reference for use by Vitalsofttech DBA’s. If you have any questions please post by clicking on the ASK A QUESTION link above.


  1.'Luis says

    Thanks for your help. I worked this problem for… three days. You might want to add to your post that the SID is case sensitive. It was my problem. I got confused with the /u01/app/oracle/product/11.2.0/xe at the end says xe when the SID is XE…

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