Application Isolation

Application Isolation is the process which ensures that the packages that we create won't interfere with each other by scanning them to determine if they are using only local resources and DLLs. Isolating an application with its support files ensures that the application always uses the version of shared files with which it was installed.

Why isolate an application?

1. Application isolation is one solution to component versioning conflicts, or DLL hell.
   ( Dll hell is caused when a newer version of dll replaces an older dll and the application ceases to work)
2. Isolation reduces versioning conflicts by modifying an application so it always loads the versions of components – such as DLLs – with which it was originally developed and tested.
3. Application isolation provides increased stability and reliability for applications because they are unaffected by changes caused by installation and ongoing maintenance of other applications on the system.
4. Resolve incompatibilities between different versions of shared components.
5. Reduce the complexity of the installation by storing COM activation data in a manifest instead of the registry.
6. Insulate the application from changes to shared components.

How to isolate an application?

Application isolation can be performed using one of these two methods.

• Assemblies and manifests
• MSI isolated components

Assemblies and Manifests:

Application isolation using assemblies and manifests is the recommended isolation method for Windows XP. Assemblies are DLLs or other portable executable files that applications require to function, and manifests are XML files that describe either an isolated application or an application's assemblies. These assemblies and manifests provide the same end result as Windows Installer isolated components, but keep all information outside of the registry and do not require the components to be installed in the same folder as the application. This reduces the chance of errors after isolation resulting from how the application was written.

MSI Isolated Components:

Application isolation using Windows Installer isolated components is best applicable for Windows 98 SE, Me, and 2000. It can also be used on Windows XP, but using assemblies and manifests is the better solution. The isolated component method copies shared files (typically DLLs) into an application's folder instead of a shared location. The application then uses these files instead of global ones, preventing modifications made by other applications from affecting the shared files. As a result, the application always uses the versions of these files with which it was deployed.

Application Isolation Using Wise Package Studio:

The Application Isolation wizard in Wise Package Studio provides a quick and easy way to isolate applications with their shared .DLL or .OCX files (support files).

The below steps describe how to implement the process using WPS.

1. Invoke the Application Isolation wizard from the side pane of Wise package studio as shown below

    

2.  Browse the .WSI or .MSI file on which the isolation has to be performed.

   

3. Choose on the isolation method and the isolation type. The next screens depend on the options selected here.

4. Choose how the process of isolation has to be taken place.

5. Isolation is ready to be performed.

6.  The updated Windows Installer file can be either the default MSI file appended with _isolated or a new MSI file or a MST file, as shown here.