The error message “ORA-01034: ORACLE not available ora-27101: shared memory” typically occurs in the context of Oracle Database and indicates that there is an issue preventing the Oracle instance from starting or accessing shared memory.
- ORA-01034: This error code indicates that the Oracle instance is not available or cannot be accessed.
- ora-27101: This is not a standard Oracle error code, but it often accompanies ORA-01034. It’s an operating system error code related to shared memory. This code can vary depending on your operating system.
To resolve this issue, you can follow these general troubleshooting steps:
Step 1: Check Oracle Services
Make sure that the Oracle services are running. You can do this using the lsnrctl status command for the listener and sqlplus / as sysdba to check the database instance status.
[oracle@amsora root]$ sqlplus / as sysdba
SQL*Plus: Release 19.0.0.0.0 – Production on Wed Sep 6 13:00:24 2023
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle. All rights reserved.
Connected to an idle instance.
SQL>
Step 2: Check Oracle Environment Variables
Verify that your Oracle environment variables (e.g., ORACLE_HOME, ORACLE_SID) are correctly set. These variables are essential for Oracle to locate the necessary files and configurations.
[oracle@oractl root]$ echo $ORACLE_HOME
/u01/app/oracle/product/19c/dbhome_1
[oracle@amsora root]$ echo $ORACLE_SID
oractl
[oracle@oractl root]$
Resolution: ORA-01034 and ORA-27101
Method 1:
Open command prompt and execute the below commands:
[oracle@oractl root]$ set oracle_sid=oractl
[oracle@amsora root]$ sqlplus /nolog
SQL*Plus: Release 19.0.0.0.0 – Production on Wed Sep 6 13:03:38 2023
Version 19.3.0.0.0
Copyright (c) 1982, 2019, Oracle. All rights reserved.
SQL> conn sys/sys as sysdba
Connected to an idle instance.
SQL> shutdown abort
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 3741317648 bytes
Fixed Size 8903184 bytes
Variable Size 721420288 bytes
Database Buffers 3003121664 bytes
Redo Buffers 7872512 bytes
Database mounted.
Database opened.
SQL>
Method 2:
Sometimes, the database will not be mounted correctly, so we need to mount it manually. For that, shut it down and start it up then mount. Log in as oracle user, then run the following commands:
[oracle@amsora root]$ sqlplus / as sysdba;
SQL*Plus: Release 19.0.0.0.0 – Production on Wed Sep 6 13:02:04 2023
Version 19.3.0.0.0
this is to delete
Copyright (c) 1982, 2019, Oracle. All rights reserved.
this is to delete
Connected to an idle instance.
this is to delete
SQL> shutdown immediate;
……….………………….
……….………………….
…………………………
SQL> startup nomount;
……………………..
………………………………
……………………………..
SQL> alter database mount;
SQL> alter database open;
SQL> exit
…………………………………….
SQL> sqlplus “/ as sysdba”
SQL> startup
this is to delete
Oracle instance started
——
Database mounted.
Database opened.
thi sis to delete
SQL>
Conclusion:
Please note that the specific steps to resolve this issue “ORA-01034: ORACLE not available ORA-27101: shared memory realm does not exist” may vary depending on your Oracle version. but we followed the steps for oracle database 19c. It’s essential to diagnose the problem thoroughly to identify the root cause and apply the appropriate solution. you can look into in-depth the issue in Oracle Official Documentation.
