Oracle - Problemas con un Triger

Hola a todos:

Tengo problemas con el siguiente triger:

CREATE OR REPLACE TRIGGER "SYSTEM"."TTY" AFTER
INSERT ON "PERSONAL" BEGIN
insert into system.personal values ( 'Pepito' );
END;

El problema que me devuelve la consola cuando realizo un "insert" es el siguiente:

SQL> insert into system.personal values ('Marcos');
insert into system.personal values ('Marcos')
*
ERROR en lÝnea 1:
ORA-00036: maximum number of recursive SQL levels (50) exceeded
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", line 2
ORA-04088: error during execution of trigger 'SYSTEM.TTY'
ORA-06512: at "SYSTEM.TTY", l

pero si en vez de disparar el triger con un insert,lo disparo con un "Update", funciona correctamente.

Alguien sabe por qué ?

Muchas Gracias y Saludos