CREATE OR REPLACE TRIGGER MY_SCHEMA.ENTLOGON_TR AFTER LOGON ON DATABASE
BEGIN
              MY_SCHEMA.SESSION_PKG.LOGON_PROC();
END;

SQL*Plus: Release 12.2.0.1.0 Production on Thu Dec 26 13:42:14 2019

Copyright (c) 1982, 2016, Oracle.  All rights reserved.

Enter user-name: system/system@VIPSTC
Last Successful login time: Thu Dec 26 2019 09:45:22 +05:30

Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production

SQL> CREATE OR REPLACE TRIGGER NETWORK_PLANNING.ENTLOGOFF_TR
  2      BEFORE LOGOFF
  3      ON DATABASE
  4  BEGIN
  5      DELETE FROM ENT_ACTIVELOGON_DATA
  6            WHERE SESSIONID = DBMS_SESSION.UNIQUE_SESSION_ID ();
  7
  8      COMMIT;
  9  END;
 10  /
CREATE OR REPLACE TRIGGER NETWORK_PLANNING.ENTLOGOFF_TR
                          *
ERROR at line 1:
ORA-01031: insufficient privileges