Joined: 06 Jun 2008 Posts: 8154 Location: East Dubuque, Illinois, USA
Because TSO has a PREFIX operand in the PROFILE command that controls whether or not to put your user id on the front of all data sets that are not fully qualified. What makes a data set fully qualified? When you put quote marks around the data set name. When you don't put quote marks around the data set name, the system will add your user id to the front of the data set name (assuming PROFILE PREFIX is set).