The DYNADSN= parameter works in almost the same way as DYNAGDG=. However, it is used for “well formed” dataset names that contain a date and time, or some other collating sequence in their name. For example, if SMF data is dumped to the datasets called PROD.SMF.Dyymmdd.Thhmmss, where yymmdd and hhmmss are dates and times respectively (therefore provide an auto-collating dataset sequence) then setting a parameter of DYNADSN=PROD.SMF will exactly work the same as GDG.
The use of the //LASTGDG file in Acquire is unchanged. It stores the last RMF interval's date and time and also the dataset name from where it came.