SAP - Systems Applications and Products in Data Processing

ORA-12560: TNS:protocol adapter error while connecting to Oracle Database through SQL Prompt

Possible reasons why you are facing the error:

1) Oracle Service has not yet started
Check:

Start Run --> Services.msc --> search for oracleservice --> Right click and start if it is stopped

2) Check if ORACLE_SID environmental variable is set and value has correct Database SID.

Right click on My computer --> Properties --> Advanced --> Environmental Variables --> Search for ORACLE_SID in User Variables for current user

3) Check parameter SQLNET.AUTHENTICATION_SERVICES value is set to NTS in sqlnet.ora

4) Check if TNS_ADMIN environmental variable is set on Database host and pointing to right directory. This should be pointing to drive:\ORACLE_HOME\network\admin

5) Check if listener is up and running. This is again in windows services or you can type the following command in command prompt for status

lsnrctl status

If you find listener is not running then type the following command

lsnrctl start