A computer system and computer program product for categorizing a virtual machine stage. A data processing system starts a virtual machine. It sets factor-stage ranges, wherein for each combination factor and stage, a corresponding range is present, and wherein each range is as broad as a reset range. It sets a frequency for sampling virtual machine metrics and samples virtual machine metrics to form a plurality of virtual machine metrics for each factor. It applies a value to each range satisfied by each virtual machine metric, to form a plurality of stage-qualifying values corresponding to a range, and sums all stage-qualifying values for each stage, to form a stage likelihood. The data processing system further selects a stage corresponding a highest stage likelihood. The data processing system determines if the current range is different from a former range. The system expands each range corresponding to the current stage.