The multiple copies represent versions of the same data set, which is archived each time it is replaced. The copies are referred to as a generation group and are a collection of data sets with the same root member name but with different version numbers. There is a base version , which is the most recent version, plus a set of historical versions . The data that the version accesses will be the current data. Positive numbers are absolute references to a historical version by its generation number.
Negative numbers are a relative reference to historical versions.
If a password is assigned, all files within a generation group must have the same password. SAS automatically applies any password that you assign to the base version to all of the versions in the group. As replacements occur, SAS will always maintain four copies. New AIR is created at time 4. New AIR is created at time 5, and the number of generations is changed to two.