BY


>>-+-------------------------------------------------------------------+-><
   |                   .-,-----------------------------------.         |   
   |                   |                 .-,---------.       |         |   
   |                   V                 V           |       |         |   
   '-BY--+-(--LISt--(----(--shar,op,--(----(--arg--)-+--)--)-+--)--)-+-'   
         '-(--DDName(ddn--)--)---------------------------------------'

BY specifies data set filtering criteria.

DDNAME(ddn): Specifies the name of the data definition (DD) statement that identifies a sequential data set or member of a partitioned data set that contains the filtering criteria to use. This is in the form of card-image records, in DFSMSdss command syntax, that contain the BY keywords that are described below.
LIST((schar,op,((arg)))): Specifies data set filtering. To select the data set for inclusion in the DEFRAG operation, all BY criteria must be met. See Filtering by data set characteristics for a full discussion of schar, op, and arg.