Some AppDNA algorithms analyze application DNA against one or more operating system (OS) images. Those algorithms:
When relevant, these algorithms interrogate the OS image DNA that has been loaded into the AppDNA database. For example, the Internet Explorer report checks the registry entries in the Windows OS image to see whether relevant ActiveX components are registered.
The analysis shows the effects of changes when applications are migrated between platforms. AppDNA provides a set of default OS images for each relevant OS family. You can also import your own custom OS images.
Algorithms that test applications for dependencies on features provided by the OS are referred to as OS image-dependent algorithms. These algorithms check a variety of OS image information, including:
Most of the OS image-dependent algorithms simply check the OS images in the target OS family. When you analyze your applications for a report that contains an OS image-dependent algorithm, AppDNA checks the information in every OS image in the relevant OS family that has been imported into AppDNA.
The algorithm results might differ for each OS image. Therefore when you view the results in one of the report views, the algorithm results and the application's overall RAG status may change depending on which OS image you select.
When you import an OS image into AppDNA, you specify whether it is a legacy or target OS image and its relationships with the other OS images that have been loaded into AppDNA. For example, suppose you are working on a migration from Windows XP to Windows 8 and your organization has standard laptop images for Windows XP and Windows 8. When you import them into AppDNA, you would define:
AppDNA then calculates and stores information about APIs, features, GPOs, and other settings that are in the legacy image but not in the target image. This is referred to as the OS image delta.
The OS image delta algorithms detect applications that rely on features in the OS image delta and are likely to fail on the target platform. When you analyze your applications for a report that contains an OS image delta algorithm, AppDNA checks the OS image delta for every pair of relevant OS images (Windows XP and Windows 8 in the example) that have been configured as legacy and target OS images for each other. Therefore when you view the results in one of the report views, the results may change depending on which legacy and target OS images you select. Typically you would set up your main (base or "gold") OS image for an OS family as the default OS image for that OS family.
Some of the OS image delta algorithms also check the application portfolio for applications that supply the missing features. The algorithm portfolio in this context is all of the applications that have been imported into AppDNA when the analysis is run. For example, suppose Windows XP supplies a particular DLL that Windows 8 does not supply by default. This means that applications that rely on that DLL will not work by default on Windows 8. However, sometimes the DLL might be installed automatically with another application.
Typically the OS image delta algorithms come in pairs:
Because the results for both algorithms in the pair depend on which other applications have been imported, the results may change if you re-analyze your applications after you have imported more applications.
By importing your own images, AppDNA can base its analysis on the images you actually use in your environment rather than the default images. You can optionally import more than one image for each OS family. This is useful when your organization has two (or more) corporate builds of the OS – one for laptops and one for desktops, for example.
After you import one of your own OS images, you specify its relationships with the other images that have been imported. For example, suppose you are working on a migration from Windows XP to Windows 8.1 and your organization has standard laptop and desktop images for both of those OSs. You would import the four images and configure them to define the Windows XP laptop image as the legacy image for the Windows 8.1 laptop image, and the Windows XP desktop image as the legacy image for the Windows 8.1 desktop image. The following diagram represents these relationships.
Then when you analyze your applications for the Windows 8.1 report, AppDNA compares the changes between the Windows XP and Windows 8.1 laptop images and between the Windows XP and Windows 8.1 desktop images. To view the reports, you choose whether you want to view the report for the laptop images or the desktop images.
You also define the default OS image or pair of OS images for each report that performs OS image analysis. You do this in OS Image Configuration Settings.
You can define more than one legacy OS. Specify legacy operating systems in the Configure Modules Wizard.