To list all of the members in partitioned data set PARTS.DATA, including any aliases, enter:

LISTDS parts.data MEMBERS

You then see something like the following:

PREFIX.PARTS.DATA
--RECFM-LRECL-BLKSIZE-DSORG
  VB    255   5100    PO
--VOLUMES--
  TSO001
--MEMBERS--
  PART1
  PART2
  PART3