One of the features that is liked most in Dynatrace is the custom measures. Custom measures give you lot of flexibility e.g. using custom measures you can count number of orders placed hourly. We use custom measures in production env. to monitor the hourly count of critical transactions. We later use the same data to calculate workload as and when needed.
Recently we got a request to monitor hourly count of a business transaction that was not being monitored till now. We created the relevant custom measure. In the live env. the custom measure starts collecting data from the time onward you create it. It does not get calculated for the existing data already stored in performance warehouse.
The beauty of Dynatrace is that you can calculate the newly created custom measure for existing data but for that you have to export the existing data in a Dynatrace session file. Once you have the session file you can import it as Offline session. There you have to create your custom measure and process configuration changes. This would do the trick, custom measure would get calculated for existing data as well.
The limitation for this feature is that Appmon is not able to handle large amounts of data. We wanted to calculate the custom measure for 1 week of production data, 1 week of production data was around 10GB, we created the custom measure and processed configuration changes, yet the measure was not calculated. When we did the same step for a single day of data i.e. around 2GB of data, it was successfully able to calculate the custom measure offline.