The GDG is nothing but a sequential kind of file.You can just use the SORT to copy the GDG from a PS file.
Here is the SORT solution for the copy.
//SORT1 EXEC PGM SORT
//SYSOUT DD SYSOUT A 4
//SORTIN DD DSN INPUT DISP SHR
//SORTOUT DD DSN AAA.BBB.OUTPUT(+1)
// UNIT SYSDA DISP (NEW KEEP)
// DCB (LRECL 100 RECFM FB
// BLKSIZE 0)
//SYSIN DD *
SORT FIELDS COPY
Thank you
Krishy