ALCOBJ. Command is used to prevent other users from accessing the data area until your operations are completed. CL 400 ver 1.0 Introduction To CL Programming. Retrieving External Attributes JOB Attributes. SYSTEM Attributes. RTVSYSVAL CHGSYSVAL. USR PROFILE. RTVJOBA CHGJOB. RTVUSRPRF CHGUSRPRF CHGPRF. CVTDAT DATE TOVAR (CL Variable) CL 400 ver 1.0