ORA-28009 connection to sys should be as sysdba or sysoper Exception in Oracle

ORA-28009 connection to sys should be as sysdba or sysoper
ORA-28009: connection to sys should be as sysdba or sysoper
Cause: Connect sys/password is no longer a valid syntax.
Action: Try connect sys/password as sysdba or connect sys/password as sysoper

ORA-28009 oracle error is raised when the sys user tries to connect without providing "as sysdba" . This s controlled by the O7_DICTIONARY_ACCESSIBILITY parameter. When this parameter value is set to FALSE, sys users experience this ORA-28009 error. Access to dictionary objects is restricted to the users with the system privileges SYSDBA and SYSOPER. Connecting as SYSDBA gives a user unrestricted privileges to perform any operation on a database or the objects within a database. Data dictionary objects is under SYS schema and is protected by O7_DICTIONARY_ACCESSIBILITY to FALSE settings