Generation Data Groups (GDGs) are group of datasets related to each other by a common name. The common name is referred as GDG base and each dataset associated with the base is called a GDG version.
Generation Data Groups or GDGs are a group of data sets which are related to each other chronologically and functionally. These related Data Sets share a unique Data Set Name.
Every GDG data set has a Generation number and Version number assigned to each data set.
For example, MYDATA.URMI.SAMPLE.GDG is the GDG base name. The datasets are named as MYDATA.URMI.SAMPLE.GDG.G0001V00, MYDATA.URMI.SAMPLE.GDG.G0002V00 and so on. The latest version of the GDG is referred as MYDATA.URMI.SAMPLE.GDG(0), previous versions are referred as (-1), (-2) and so on. The next version to be created in a program is refered as MYDATA.URMI.SAMPLE.GDG(+1) in the JCL.
Generation Number -> GaaaaVnn aaaa is between 0000 to 9999 nn is between 00 to 99.