You must set scripts to point to the new Oracle home location.
After you upgrade Oracle Database to a new release, you must ensure that your
oratab file and any client scripts that set the value of
ORACLE_HOME point to the new Oracle home that is created for the new Oracle Database release. DBUA automatically points
oratab to the new Oracle home. However, you must check client scripts regardless of the method you use to upgrade.
If you upgrade your database manually, then you must log in as the Oracle installation owner for the new Oracle Database release, and update the
oratab file manually. The location of the
oratab file can vary, depending on your operating system.
Oracle Database Administrator’s Guide for information about setting operating system environment variables
My Oracle Support: Find or Create Oratab File (Doc ID 394251.1)