When an application layer creates or modifies files they are stored in the writeable sublayer. If the layer is then reset, the files in the writeable sublayer are deleted. This behavior lets you reset an application to the default state if settings become corrupted. However, many applications create data files that you do not want to lose when a layer is reset. These files need to be stored on the base file system and not in the layer to prevent potential loss.
For example, you create and activate a Microsoft Word layer. You do not create any layer exclude entries, global exclude entries, or data layers to redirect .doc files from the layer's writeable sublayer. You then activate the Microsoft Word layer and use it to create .doc files that you save on the computer's hard drive. If you then reset the Word layer, all of the .doc files you created are lost.
Table: Methods to prevent data loss
You can create a data layer that captures the application data files that have specified extensions or that are in a specified directory. A data layer captures the application data so that it is not redirected to the writeable sublayer of the application layer.
Layer exclude entry
You can create layer exclude entries for an application layer. A layer exclude entry can be a file extension or a directory. Application data that matches the layer exclude entry is saved in the base file system.
Global exclude entry
You can create global exclude entries for a computer. A global exclude entry can be a file extension or a directory. A global exclude entry applies to all layers on a computer. Application data that matches the global exclude entry is saved in the base file system.
You can save the application data of a virtualized application to a non-local storage device, such as a network share. The data is then not redirected to the application layer.
New reset point
You can copy the data from the writeable sublayer to the read-only sublayer using a new reset point.