You have learned that you can keep an audit trail to
track observation updates made to an individual data set in place.
However, if you replace the data set, the audit trail is lost. Generation
data sets enable you to maintain multiple versions or generations
of a SAS data set. A new generation is created each time the file
is replaced.
By default, generation
data sets are not in effect. As the SAS data set A is replaced, there
are two copies of A in the SAS library. When the DATA step completes
execution, SAS removes the original copy of the data set A from the
library.
When generation data
sets are in effect and the SAS data set A is replaced, there are two
copies of A in the SAS library. When the DATA step completes execution,
SAS keeps the original copy of the SAS data set A in the library and
renames it.
Each generation of a
generation data set is stored as part of a generation group. Each
generation data set in a generation group has the same root member
name, but each has a different version number. The most recent version
is called the base version. When generations are in effect, SAS filenames
are limited to 28 characters. The last four characters are reserved
for the version numbers.
Note: Generation data sets are
not supported on VMS.