Set the Oracle home environment variable in Windows platform

Set the Oracle Home environment variable in Windows platform:
1. Set at Command Prompt Level( temporary at session)
2. Set at user level (with Environment variable setting)
3. Set at system level(with Environment Variable Setting)

Set at Command Prompt Level
Set the destination according to it where oracle is installed and Oracle sid defined as the instance name.
Open the command Prompt window and set the following paths will set your Oracle Environment variables.

SET ORACLE_BASE=C:\oracle
SET ORACLE_HOME=%ORACLE_BASE%\product\12.2.0
SET ORACLE_SID=test
SET PATH=%ORACLE_HOME%/bin;%PATH%


Set at user level
When you login with user, the Oracle Home environment variable is already set when you login with user by setting them in Window Environment Variable Setting.
Search Environment variable in Start menu –> Open system Properties and go to environment Variables
Edit the User and System level setting depend upon your need. If you want set Oracle Home at user level then use upper window and if you set at system level then use below window as highlighted:

Press NEW or EDIT button as shown below in following snapshot:
Set new environment variable ORACLE_HOME and its value “C:\oracle\product\12.2.0\dbhome_1”
and edit PATH variable and append its value “C:\oracle\product\12.2.0\dbhome_1\bin”.