Solved – Why did I get ORA-27101 Shared Memory Realm does not exist?

When trying to connect to the database using sqlplus, I am getting the “ORA-27101 Shared Memory Realm does not exist” error. What is the cause and how do I resolve this?

The following error is returned when invoking sqlplus.

    $SQL*Plus: Release 12.1.2 – Production on Mon May 10 21:32:30 2015

    Copyright (c) 1982, 2015, Oracle. All rights reserved.

    Enter user-name: vst_dba
    Enter password:
    ERROR:
    ORA-01034: ORACLE not available
    ORA-27101: shared memory realm does not exist

Cause

According to the lookup from oerr, this could be due to:

    27101, 00000, “shared memory realm does not exist”
    Unable to locate shared memory realm
    Verify that the realm is accessible

This is usually due to an invalid ORACLE_HOME or ORACLE_SID varaible set at the OS level.

Solution

First verify that the database that you are trying to connect to is up and running.

    $ps -ef|grep smon
    oracle 43526 1 0 21:13 ? 00:00:00 ora_smon_EQ1

Next check the environment value for the ORACLE_HOME and ORACLE_SID.

    $echo $ORACLE_SID
    $EQ1
    $echo $ORACLE_HOME
    $/opt/app/oracle

Since the ORACLE_SID value is incorrect export the correct value and try connecting again.

    $export ORACLE_SID=EQ2

Then invoke sqlplus

    $sqlplus
    SQL*Plus: Release 12.1.2 – Production on Mon May 10 21:42:11 2015

    Copyright (c) 1982, 2015, Oracle. All rights reserved.

    Enter user-name: vst_dba
    Enter password:
    Connected.

Issue resolved.

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