SQL> connect scott/tiger
Connected.
SQL> grant insert on scott.dept to mag;

Grant succeeded.

SQL> connect mag/mag
Connected.
SQL> create or replace trigger trigger_t1
  2  after insert on dept
  3  for each row
  4  begin
  5  insert into scott.dept values (:new.deptno,:new.dname,:new.loc);
  6  end;
  7  /

Trigger created.

SQL> select * from dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON

SQL> select * from scott.dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON

SQL> insert into dept values
  2  (50,'GENOME','CHarles');

1 row created.

SQL> commit;

Commit complete.

SQL> select * from scott.dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON
        50 GENOME         CHarles

SQL> select * from dept;

    DEPTNO DNAME          LOC
---------- -------------- -------------
        10 ACCOUNTING     NEW YORK
        20 RESEARCH       DALLAS
        30 SALES          CHICAGO
        40 OPERATIONS     BOSTON
        50 GENOME         CHarles