Conclusions
•Good application design and good
process design do not rewrite history, and do not re-summarize
the same history repeatedly.
•Purging old data should have
almost no effect on day-to-day performance if the application is
well-designed and the query execution plans are well-tuned and
robust. (Purging can save disk and make backups, recoveries, conversions,
other DBA tasks easier and faster, though.)