Contents Lab128 - Tools for Advanced Oracler Tuning and Monitoring. Reference Guide.

Statistics Correlation

The Statistics Correlation window analyzes the correlation between two statistics by drawing one statistic as a function of another. Each point on the correlation diagram has the same time; the X coordinate represents value of Statistic1; the Y coordinate - value of Statistic2. To help find the location of a point in time, they are colored with progressively changing color, from violet to red, traversing all the colors of rainbow in between.

The statistic correlation diagram helps to identify and analyze the correlation between statistics, identifying the limitation of the system or uncovering performance problems.

Viewing options.

The Statistics Correlation window has a correlation diagram in the upper part and a Charts panel in the lower part. Nothing is shown in the correlation diagram unless at least two statistics are added in the Charts panel. You can add statistics in one of two ways:

  1. Using the "Quick Y Pick" and "Quick X Pick" drop-down lists;
  2. Switching to another window that contain charts. Right-click on the chart and choose the "Merge Graph to Other Page" item in the drop-down menu.

Once statistics are added, the correlation diagram shows up. The upper statistic is used for Y axis, the lower one - for X axis. By default, the correlation diagram automatically scales both the vertical and horizontal axes. The scale can be manually changed by right-clicking on the diagram and dragging vertically while holding the button down. The diagram rescales as the mouse pointer moves. To return back to autoscale mode, open the pop-up menu by right-clicking and select "Auto Scale".

The time range represented in the Correlations diagram is generally defined by the time interval of statistics in the Charts panel. If the time interval gets too big, Lab128 limits it to 1 hour for performance reasons. The effective time interval is highlighted in light yellow in the charts and indicated in the header line of the correlation diagram. It is possible to select a time interval to be used in the correlation diagram. Select a time interval in the Charts panel as described in the Detailed Chart help. To clear a selection, press the "Clear Selection" button on the Charts panel or use the pop-up menu.

If you need to locate a specific point, click inside the graph's selected area. The dashed line on the chart will appear and the corresponding point on the correlation diagram will be marked with a cross sign. This also works in reverse: click on a data point in the correlation diagram and the corresponding point will be shown as a dashed line on the graphs.

Note. You can have more than two statistic charts in the Charts panel, but only the first two are used for Correlation. Since it is easy to change a statistic's chart position by either dragging it or through the pop-up menu, it may be useful to have many charts in the Charts panel and then experimenting with different correlation combinations by changing their positions.