How to Fix ORA-12162 TNS:net service name is incorrectly specified Error in Oracle?

sometimes  the oracle profile is not prepared correctly and this give so many errors and you should go direct to directory of SqlPlus to start DB

/u01/app/oracle/product/11.2.0/dbhome_1/bin

./sqlplus sys/password as sysdba;

the following error will arises

ORA-12162 TNS:net service name is incorrectly specified

Cause

This arises if you have not set ORACLE_HOME and ORACLE_SID.

Solution

you can fix it by setting the ORACLE_HOME and ORACLE_SID as following

> export ORACLE_HOME=/u01/app/oracle/product/11.2.0/dbhome_1
> export ORACLE_SID=ECMTEST

and try to start the DB 

./sqlplus sys/password as sysdba;
sql> startup force;