TSO LOGON was unsuccessful in performing one of the indicated operations (I/O, OBTAIN, or OPEN). In the message text, ddname refers to the DD statement defining the data set being referenced when the error occurred. The message text also includes the user identification (userid) of the user being serviced when the error occurred and the procedure name, ppp, which the user had selected unless they are unknown to TSO LOGON at the time of the error.