This article describes the workflow, which can cause deletion of files in subassembly files.
Prior to SOLIDWORKS 2013, choosing to delete a component from a subassembly would delete the subassembly from the top assembly file, instead of the part component. In SOLIDWORKS 2013 and 2014, this behavior was changed by allowing users to delete part components from the top assembly file. However, users who are used the workflow prior to SOLIDWORKS 2013, can find themselves with deleted components in assembly files, which act as a subassembly in a top assembly.
In order to prevent this issue, SOLIDWORKS 2015 has added a new implementation of the new Confirm Delete Dialog Box, which can be seen below.
When a component is deleted from a subassembly in a top assembly, a dialog box asks if the subassembly file or the selected components should be deleted. Choosing to delete the subassembly will delete the subassembly that includes the selected components from the top assembly, while choosing to delete the selected component will delete the selected component from the subassembly file.