As far as I know, it is not possible to debug a PL/SQL package in normal compiled mode. It has to be compiled in INTERPRETED mode to be debugged. My *guess* is that PL/SQL developer is doing this for you behind the scenes. My further guess is that it is trying to do this as the user you are connecting with. It is either trying to ALTER PACKAGE x COMPILE DEBUG or it is trying to do an ALTER SESSION/SYSTEM to set PLSQL_DEBUG to true. In either case, I'm guessing that your user simply does not have the proper grants to be able to do that.