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One of the most important concepts of Delft-FEWS is that always the latest forecast data is available to be used. In a typical operational Delft-FEWS forecasting system, new data is constantly imported, while older data is no longer relevant and can be removed. For a lot of database tables in fews master-controller the central Delft-FEWS database, the rows (records) in the database have an expiryTime column specifying when the data can be removed. The removal is done by the so-called RollingBarrel process. It will remove any data for which the expiry time is exceeded.
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Timeseries in the database without taskruns are referred to as "orphaned timeseries". Note that simulated timeseries are not meaningful without taskrun information and should never be orphaned. Only external timeseries can be orphaned, but without taskruns they can not be amalgamated (merged) any more. In order to preserve taskruns longer than the default of ten days, the taskruns expirytime should be increased. See also ImportAmalgamate for more information on amalgamate.
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