An allocation of a GDG data set refers to the same data set for the life of the job (or TSO/E logon session), even if another generation is added during the job, unless the bit S99GDGNT is set in the FLAGS1 field of the request block. When this bit is on, the system issues a LOCATE to find the GDG base level. See Flags (S99FLAG1) for a description of the bit, and Table 3 for an example using S99GDGNT. See z/OS MVS JCL User's Guide for more information about GDG data sets.