A generation data group is a collection of chronologically related data sets that have the same data set name. To add a generation to a generation data group or retrieve a generation, specify the generation data group name followed by the generation number. A zero is the current generation of the group, a negative number (for example, -1) is an older generation, a positive number (for example, +1) is a new generation that does not exist yet.
Examples
//NEWGDS DD DSNAME=GDS(0),DISP=(NEW,CATLG,DELETE),
// UNIT=3380,VOLUME=SER=334455,SPACE=(CYL,20)
//OLDGDS DD DSNAME=GDS(-1),DISP=OLD
//NEWER DD DSNAME=GDS(+1),DISP=(NEW,CATLG,DELETE),
// UNIT=SYSDA,VOLUME=SER=222333,SPACE=(TRK,15)
//ALLG DD DSNAME=GDS,DISP=OLD
//SMSGDG DD DSNAME=A.B.C(+1),DATACLAS=DGDG1,DISP=(NEW,KEEP)