A viewer will open for each data representation (see Using HPjmeter to Analyze Profiling Data (page 29) for an example profiling viewer).

2.Click on one of the viewers to make it active.3.Two ways exist to create a combined set of comparable data:•In one viewer, click File→Compare , or•click the Compare button .

The Compare window opens, and you can now see the other file to compare your first file against.

4.Click the file name that you want to compare against.5.When the file is highlighted, click the Compare button.

A new profile viewer opens that presents the selected data sets in comparison to one another.

NOTE: For alternate access when you have multiple viewers open, click the button to bring the console to the top. The console lists all open sessions and data sets. For data sets, click the data representation to bring the already open viewer to the top.

If the viewer has been closed, but the data representation is still listed in the console, double-clicking the data representation opens a new viewer.

Scaling Comparison Data

At times it is not possible to run performance testing benchmarks under identical conditions. For example, the load may be slightly different, or the measurement duration may differ, or you may want to compare the same activity at different times of the day or week. To compensate for these differences, you can scale one set of data to more closely match the other set.

Scale and Scale Special are available from the Edit menu on the profiling viewer when comparing two profiling data files. Use these scale options when the data files that you are comparing are unequal in some way.

For example, imagine a scenario where you are able to generate a constant load on your systems, but one profile represents 10 minutes of application activity and the other only 5 minutes. You can use Edit →Scale Special to set and apply a factor of 2 to the shorter time period, which normalizes the 5–minute data set to 10 minutes for easier presentation and interpretation.

Or, suppose that you want to look at activity for a particular application during peak business hours and compare it to a relatively quiet period at night. You know that the number of transactions will differ, so how do you compare the amount of work done for each transaction?

Open a profiling viewer with the peak time data. Open another viewer with the night data. In the peak time viewer, click File→Compare to open a profiling viewer with the comparison data.

In the comparison viewer, select Metrics→Code/CPU→Method Call Count. Click to select a known method that represents a unit of work or a transaction. Then click Edit →Scale from the

72 Profiling Applications