hi everyone. I which to thank you before for your help.
I now realyze my (many) mistakes. :) 1st of all i misunderstood the use of the "database monitor" directive. I did not read correctly the manual, and I tought this directive was applyed to the previous database and i I apply my ACL below this line. So my security was not applyed on the right db/directory
2nd I misunderstand too the use of the dn.<scope> operand. As Gavin point it out.
Now everything works fine. Thanks to all. of you.
Guillaume