Gaps in performance data are corrected for through data transformations and conversion. A raw sequence is transformed by correction logic into an interval sequence by partitioning a performance monitoring period into equal intervals and assigning values based on the raw sequence. Locality sequence entries can indicate whether the interval sequence relies on estimation. The interval sequence is converted into an absence length sequence whose entries indicate null value periods in performance data. Conversion includes generating a presence sequence from the interval sequence, and deriving the absence length sequence from the presence sequence, by using a set-based algorithm or other mechanism. Excessive absence length values support treating intervals as downtime for the machine. Correction logic may include a stored procedure residing in a database, for example, which produces the absence length sequence without using a procedural language.