Patent Number: 
Section: claims

1. A controller-executed method for detecting changes in a performance metric in an automated information technology (IT) management system comprising:defining, using a hardware processor, segments as sets of contiguous time samples wherein time samples within a particular segment are mutually more similar in terms of performance metric behavior than time samples in previous and subsequent segments;determining, using the hardware processor, for each of the segments, a weighted cost based on a compactness parameter and a sum over a plurality of time samples derived from a difference between a metric value for each of the plurality of time samples and an average value of the performance metric for the plurality of time samples; andfinding, using the hardware processor, a segmentation that minimizes a sum of the weighted costs for the segments. 2. The method according to claim 1 wherein determining the weighted cost for each of the segments is based on the compactness parameter and a sum over the plurality of time samples of a square of the difference between the metric value for each of the plurality of time samples and the average value of the performance metric for the plurality of time samples. 3. The method according to claim 1 wherein the compactness parameter is based on an anomaly definition. 4. The method according to claim 1 further comprising:detecting changes in service conditions using the segmentation; anddetecting changes in cyclic performance behavior using the segmentation. 5. An automated information technology (IT) management system comprising:a computer comprising:a hardware processor to execute:logic to define segments as sets of contiguous time samples wherein time samples within a particular segment are mutually more similar in terms of performance metric behavior than time samples in previous and subsequent segments;logic to determine, for each of the segments, a weighted cost based on a compactness parameter and a sum over a plurality of time samples derived from a difference between a metric value for each of the plurality of time samples and an average value of the performance metric for the plurality of time samples; andlogic to find a segmentation that minimizes a sum of the costs for the segments. 6. The system according to claim 5 further comprising:a response tool executable in the computer to respond to detection of changes in the performance metric. 7. The system according to claim 5:wherein the computer further comprises:logic to determine the weighted cost wi,j for each of the segments according to an equation:      w          i      ,      j        =                    ∑                  t          =          i                j            ⁢                        (                                    X              t                        -                          μ                              i                ,                j                                              )                2              +    λ  wherein Xt is the metric value, μi,j is the average value of the performance metric, and λ is the compactness parameter. 8. The system according to claim 5:wherein the logic to find the segmentation is based on a compactness parameter λ, and wherein the performance analyzer further comprises:logic to define an anomaly determined by a length m of an anomalous segment and deviation of the anomalous segment from normal behavior;logic to determine the compactness parameter λ according to the defined anomaly; andlogic to scale the compactness parameter λ by an estimate of a data variance according to an equation:      λ    =                            m          ⁡                      (                                          μ                n                            -                              μ                m                                      )                          2                    2        ⁢                                  ⁢        K              ,wherein a segment is a mixture of two distributions comprising a first distribution of mean μn with n time samples and a second distribution of mean μm with m time samples, and K is the estimate of data variance. 9. The system according to claim 5:wherein the computer further comprises:logic to determine the weighted cost wi,j for each of the segments according to equation:      w          i      ,      j        =                    1        K            ⁢                        ∑                      t            =            i                    j                ⁢                              (                                          X                t                            -                              μ                                  i                  ,                  j                                                      )                    2                      +    λ  wherein Xt is the metric value, μi,j is the average value of the performance metric, λ is the compactness parameter, and K is estimated data variance. 10. An article of manufacture comprising:a non-transitory computer-readable storage medium storing computer readable program codes executable by a computer for detecting changes in a performance metric, the computer readable program codes comprising:code causing the computer to define segments as sets of contiguous time samples wherein time samples within a particular segment are mutually more similar in terms of performance metric behavior than time samples in previous and subsequent segments;code causing the computer to determine, for each of the segments, a weighted cost based on a compactness parameter and a sum over a plurality of time samples derived from a difference between a metric value for each of the plurality of time samples and an average value of the performance metric for the plurality of time samples; andcode causing the computer to find a segmentation that minimizes a sum of the weighted costs for the segments.