Error ora-01034 ora-27101 linux-x86_64

Error Symptom

Enter user-name: bnsuser/bnsuser@stlbas
ERROR:
ORA-01034: ORACLE not available
ORA-27101: shared memory realm does not exist
Linux-x86_64 Error: 2: No such file or directory

Reason:

1. Check ORACLE_HOME is set correctly in listener file or not.
2. Check parameter file name with grep pmon (SID name) is same or not 
3. Check ORACLE_SID

[oracle@stlbasprod2 dbs]$ ps -ef | grep smon
oracle   11654     1  0 11:33 ?        00:00:00 ora_smon_STLBAS
oracle   11830  9978  0 11:45 pts/2    00:00:00 grep smon


[[oracle@stlbasprod2 dbs]$ ps -ef | grep pmon
oracle   11638     1  0 11:32 ?        00:00:00 ora_pmon_STLBAS
oracle   11837  9978  0 11:46 pts/2    00:00:00 grep pmon
[oracle@stlbasprod2 dbs]$

[oracle@stlbasprod2 dbs]$ echo $ORACLE_SID
STLBAS

Action:

1. Change the parameter file name initstlbas.ora to initSTLBAS.ora
2. stop and start the listener
3. shutdown the Database then startup
4. try to connect Database using normal user

Enter user-name: bnsuser/bnsuser@stlbas

Connected to:
Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - 64bit Production
With the Partitioning, OLAP and Data Mining options

SQL>