Shared Memory Realm Does Not Exist

 ORA-01034 & ORA-27101: Shared Memory Realm Does Not Exist

ORA-12701 may occur from various reason . According to the oracle doc's  ,

ORA-27101 :  shared memory realm does not exist

Cause  : Unable to locate shared memory realm .

Action  : Verify that the realm is accessible .

ORA-27101 and ORA-01034  combined may occurs in various scenarios .The main reason for this error is that the database is not up. When we try to connect with oracle database or sometimes during installation we may get this error . We may face this error in some other scenario's too . Here are few possible scenario's (  some scenario's are from window platform and some are from Linux  platform )

Case 1 :  When try to connect with normal user we get the error as

C:\>sqlplus

SQL*Plus: Release 11.2.0.1.0 Production on Mon Feb 6 11:22:08 2012

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

Enter user-name: scott

Enter password:

ERROR:

ORA-01034: ORACLE not available

ORA-27101:  shared memory realm does not exist

Process ID: 0

Session ID: 0 Serial number: 0

To solve this issue , set the ORACLE_SID and start the database using the "sys" user as sysdba and start the database ,

C:\>set ORACLE_SID=noida

C:\>sqlplus sys/xxxx@noida as sysdba

SQL*Plus: Release 11.2.0.1.0 Production on Mon Feb 6 11:25:13 2012

Copyright (c) 1982, 2010, Oracle.  All rights reserved.

Connected to an idle instance.

SQL> startup

ORACLE instance started.

Total System Global Area  535662592 bytes

Fixed Size                  1375792 bytes

Variable Size             331350480 bytes

Database Buffers          197132288 bytes

Redo Buffers                5804032 bytes

Database mounted.

Database opened.

Case  2 :  On a system with multiple IP addresses, when we connect with sqlplus locally on the server  (i.e. "sqlplus user/password") everything is OK, but connecting through a TNS alias, either from the network or locally on the server, we get the the following errors :

$ sqlplus user/password@db_alias

ERROR:

ORA-01034: ORACLE not available

ORA-27101: shared memory realm does not exist

SVR4 Error: 2: No such file or directory

We need to Manually startup the database or check whether the listener is started or not . So either connect as

$export ORACLE_SID=noida

$ sqlplus sys/password as sysdba

SQL>startup

or

check the status of listener if not started then start the listener  as

$lsnrctl

lsnrctl> stop

lsnrctl>start

lsnrctl>exit

$export ORACLE_SID=noida

$sqlplus sys/password@noida as sysdba

SQL> startup

Case 3 :  Make sure while connecting, that the ORACLE_SID and ORACLE_HOME is correctly set . There should not be trailing trash in ORACLE_HOME  path . So, set ORACLE_SID  before connecting as :

Linux  :

$export ORACLE_SID=noida

$sqlplus sys/xxxx@noida as sysdba

SQL> startup

Window  :

C:\> set ORACLE_SID=noida

C:\> sqlplus sys/xxxx@noida as sysdba

C:\> startup

Case 4 :   Sometimes in case of window ,  if event log is full , then we get this error . So delete the event logs and try to connect again .

Enjoy     :-)