Volume Shadow Copy Service (VSS) is a Windows service for capturing and creating snapshots called shadow copies. VSS, which operates at the block level of the file system, provides a backup infrastructure for Microsoft operating systems. VSS writer - Each VSS-aware application installs its own VSS writer to a computer during the initial installation. VSS requestor - Any application that needs to quiesce data for capture can play the role of VSS requestor. This announcement instructs each VSS writer to perform any post-backup tasks necessary so the computer and its applications can return to regular operation. This was first published in, april 2012.