ASTEX Group appear in two different formats, DCGnnn and Dnnnnn.
The default for ASTEX defined CGROUPs is to use DCGxxx, where xxx represents the storage director ID. Occasionally, the 3 position xxx is not sufficient to prevent duplicates or the storage director ID is greater than 999. In those instances, the "CG" is dropped and the format becomes Dxxxxx. Note: if you do not like the names generated by ASTEX, you may specify your own names via the DEFINE CGROUP parameter.