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ORA-27101: shared memory realm does not exist
- November 8, 2021
- Posted by: admin
- Category: Oracle DBA
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ORA-27101: shared memory realm does not exist

Cause: Unable to locate shared memory realm
Action: Verify that the realm is accessible
There may be 2 scenarios, which may lead you to encounter ORA-27101
1) Invalid ORACLE_HOME and ORACLE_SID
2) Database is down
[oracle@192 ~]$ sqlplus scott/tiger SQL*Plus: Release 10.2.0.1.0 - Production on Wed May 22 16:48:05 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. ERROR: ORA-01034: ORACLE not available ORA-27101: shared memory realm does not exist Linux Error: 2: No such file or directory
Scenario 1: Invalid ORACLE_HOME and ORACLE_SID:
ORA-27101 is usually due to the invalid ORACLE_HOME and ORACLE_SID parameters at OS level. You should investigate that ORACLE_HOME and ORACLE_SID are set correctly, and ORACLE_HOME should be without trailing slash.
[oracle@192 ~]$ echo $ORACLE_HOME /data/app/oracle/product/10.2.0/db_1 [oracle@192 ~]$ echo $ORACLE_SID testdb
In our case ORACLE_SID was not correct, we need to export ORACLE_SID to the valid one which is ora19c
[oracle@192 ~]$ export ORACLE_SID=ora10g [oracle@192 ~]$ sqlplus scott/tiger SQL*Plus: Release 10.2.0.1.0 - Production on Wed May 22 16:52:11 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options
Scenario 2: Database is down:
You may also face it when the database is down, to solve ORA-27101 you may have to start the database only
[oracle@192 ~]$ sqlplus sys/sys as sysdba SQL*Plus: Release 10.2.0.1.0 - Production on Wed May 22 17:07:38 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to an idle instance. SQL> startup ORACLE instance started. Total System Global Area 1224736768 bytes Fixed Size 1219112 bytes Variable Size 167773656 bytes Database Buffers 1040187392 bytes Redo Buffers 15556608 bytes Database mounted. Database opened.
ORA-27101: shared memory realm does not exist

Cause: Unable to locate shared memory realm
Action: Verify that the realm is accessible
There may be 2 scenarios, which may lead you to encounter ORA-27101
1) Invalid ORACLE_HOME and ORACLE_SID
2) Database is down
[oracle@192 ~]$ sqlplus scott/tiger SQL*Plus: Release 10.2.0.1.0 - Production on Wed May 22 16:48:05 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. ERROR: ORA-01034: ORACLE not available ORA-27101: shared memory realm does not exist Linux Error: 2: No such file or directory
Scenario 1: Invalid ORACLE_HOME and ORACLE_SID:
ORA-27101 is usually due to the invalid ORACLE_HOME and ORACLE_SID parameters at OS level. You should investigate that ORACLE_HOME and ORACLE_SID are set correctly, and ORACLE_HOME should be without trailing slash.
[oracle@192 ~]$ echo $ORACLE_HOME /data/app/oracle/product/10.2.0/db_1 [oracle@192 ~]$ echo $ORACLE_SID testdb
In our case ORACLE_SID was not correct, we need to export ORACLE_SID to the valid one which is ora19c
[oracle@192 ~]$ export ORACLE_SID=ora10g [oracle@192 ~]$ sqlplus scott/tiger SQL*Plus: Release 10.2.0.1.0 - Production on Wed May 22 16:52:11 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to: Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options
Scenario 2: Database is down:
You may also face it when the database is down, to solve ORA-27101 you may have to start the database only
[oracle@192 ~]$ sqlplus sys/sys as sysdba SQL*Plus: Release 10.2.0.1.0 - Production on Wed May 22 17:07:38 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to an idle instance. SQL> startup ORACLE instance started. Total System Global Area 1224736768 bytes Fixed Size 1219112 bytes Variable Size 167773656 bytes Database Buffers 1040187392 bytes Redo Buffers 15556608 bytes Database mounted. Database opened.