How to find the sid of oracle database?

Following are the different ways to find the SID of ORACLE database.

1. Without connecting to database 

WINDOWS:

If Environment Variables are set, then use below command in windows command prompt.

echo %ORACLE_SID%

If Environment Variables are not set, then you can check the window's service for a service named OracleService<sid_name>. 

UNIX/LINUX:

If Environment Variables are set, then use below command in command line.

echo $ORACLE_SID

If Environment Variables are not set, then you can check the /var/opt/oracle/oratab file on UNIX and the /etc/oratab file on LINUX.

2. After connecting to database

Connect with SYS or SYSTEM user. Execute any following SQL statement to find the ORACLE_SID

• SHOW PARAMETER INSTANCE_NAME 
• SELECT INSTANCE FROM V$THREAD; 
• SELECT SYS_CONTEXT('USERENV','INSTANCE_NAME') FROM DUAL; 

How to find the sid of oracle database