A set of records that has been committed to a Record Store instance is a record generation.

For example, if you perform a full file system crawl, all the records returned from the crawl are written to the Record Store and a commit is done. After the commit is done, the Record Store has one generation of records. A subsequent crawl, either full or incremental, results in a second generation of records.

Each record that is read in contains a unique ID. CAS uses that unique ID as the value of the idPropertyName Record Store configuration property.

If a record already exists with that unique ID during later CAS crawls, then the later version replaces the earlier one. This ensures that when you run an incremental crawl, you always get the latest version of any given record.

A record generation is removed from a Record Store instance by the clean task after the generation becomes stale. A stale generation is a generation that has been in a Record Store instance for a period of time that exceeds the value of the generationRetentionTime Record Store configuration property. I

A stale generation is retained in several exception cases: