java.sql.SQLRecoverableException: ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory
This error is occurring while trying to establish the database connection,This error occur due to
1) Invalid ORACLE_HOME and ORACLE_SID or
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 $ORACLE_HOME
/u01/app/oracle/product/10.2.0/db_1
[oracle@192 ~]$ echo $ORACLE_SID
testdb
In our case ORACLE_SID was not correct, we need to export ORACLE_SID to the valid one which is ora10g
[oracle@192 ~]$ 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.