You can logically connect or concatenate (link together) sequential or partitioned data sets (PDSs or PDSEs) for the duration of a job step. To concatenate data sets, omit the ddnames from all the DD statements except the first. The data sets are processed in the same sequence as the DD statements defining them.
//INPUT DD DSNAME=FGLIB,DISP=(OLD,PASS)
// DD DSNAME=GROUP2,DISP=SHR