The allocation can be patterned after a previously allocated generation in the same group, by specifying DCB attributes for the new generation, described as follows.

If you are using absolute generation and version numbers, DCB attributes for a generation can be supplied directly in the DD statement defining the generation to be created and cataloged.

If you are using relative generation numbers to catalog generations, DCB attributes can be supplied:

1. By referring to a cataloged data set for the use of its attributes.
2. By creating a model DSCB on the volume on which the index resides (the volume containing the catalog). Attributes can be supplied before you catalog a generation, when you catalog it, or at both times.

   Restriction: You cannot use a model DSCB for system-managed generation data sets.

3. By using the DATACLAS and LIKE keywords in the DD statement for both system-managed and non-system-managed generation data sets. The generation data sets can be on either tape or DASD.
4. Through the assignment of a data class to the generation data set by the data class ACS routine.

WARNING: IBM strongly recommends that you specify a new generation by a relative generation number (and allow the system to compute the G0000V00 number). This avoids the possibility of creating a generation number that exceeds 9000 for any data set in the GDG, which might cause an ambiguity regarding the correct chronological order. This could happen, for example, if you specified a fully-qualified name and used the first two digits of the number to represent the year. If, however, you must specify a fully-qualified G0000V00 name, you should include a DD statement for the GDG base name, to provide data set integrity on that base.