If data age storage limiting mode is used, then the sweep interval will be the data age divided by this value.
Sweep intervals do not fall on any defined moment in time.
If you have chosen to delete data, the only guarantee is that records stored since the parameter modification and newer than the limit are kept. Records that are newer than the limit BUT older than the parameter modification may be deleted.
Older records will be swept eventually and it is seldom worthwhile to focus on the value of the Sweep Interval.
If storage limiting is in effect, then regardless of any property settings, the maximum interval between sweeps will be no greater than 365 days and no less than one hour.
Section: System
Default: HistorianDataAgeSweepIntervalDivisor = 4
*No restart required (Settings.Dynamic property)
The term "sweep interval" is slightly misleading in that the interval actually sets the time between creation of new record sequences, "blocks", in the Historian. During a sweep, entire record sequences older than the number of days or records to keep, are removed. Changes to the sweep interval do not affect existing record sequences. Sweeps may occur on any of application startup, workstation becomes the server, and again after the next interval since the last sweep.
Sweeping is done based on when data was recorded, which may differ from the data timestamp, especially in the case of manually entered data. Sweeping is based only on the age of the record sequence and is not done on a tag-by-tag basis, nor do sweep intervals line up with calendar dates such as January 1st.
Again, if you have chosen to delete data, the only guarantee is that records newer than the limit are kept and that limit may be set to any length of time. Older records will be swept eventually.
