Layer patches provide a mechanism to make small, incremental updates to an existing application layer. Layer patches reduce the need to create a new layer to provide an application update. A layer patch file contains the changes between two versions of an application. Layer patches let you update layers without distributing a completely new layer.

For example, an existing Firefox 3.01 virtual software layer can be updated to version 3.02 by applying a small patch file.

When applying a patch, you can select to keep the previous layer and create new layer with the updated versions. This feature can simplify application migration by providing access to both versions. You can also copy all of the data and the settings that are stored in the writeable sublayer to the new version.

Patch files must be applied incrementally. If you create multiple patches, they must be applied in the order they were created.

To create a layer patch file you need a layer that contains the existing version of an application. This layer must have the same GUID as the layer distributed in your environment. You also need a second layer that contains the updated version of the same application. For example, Firefox 3.01 in the first layer and Firefox 3.02 in the second.

For a detailed explanation of the patch creation process, see the following article on Symantec Connect:

Exploring the layer patch feature

VIDEO: Creating layer patches

After a patch is applied, Windows Shortcut files (.LNK) that are contained in the writeable sublayer of the previous version are removed. Any new shortcuts in the new version are available. This process helps prevent unusable shortcuts from being left after an upgrade.