KnapSac consists of Client software which runs on OpenVMS and Server software which runs on Windows. The Client software uses standard OpenVMS command syntax for specifying which file are to be backed up or restored. The Server software consists of a server program which runs as a Windows service and a control program which controls the service and also manages the KnapSac configuration file.  The configuration file describes details of each KnapSac service which runs on the Windows computer. KnapSac Client Program The KnapSac Client program provides a OpenVMS user with commands to save/restore files between OpenVMS and Windows and also has commands to display a directory list of the files that are present on the Windows computer. The KnapSac Client supports image mode and file mode backups and includes optional data compression to minimize backup times and storage requirements. KnapSac Windows Service The KnapSac Windows Service communicates with the Client program using TCP/IP.  The Service waits for commands from the Client and then takes appropriate actions based on the commands, such as: Accept one or more files from OpenVMS and store them in a KnapSac pacset on Windows Retrieve one or more files from a KnapSac pacset and send the files to OpenVMS Provide a list of the files which are present on the Windows computer Provide a list of files which are present in a KnapSac pacset Multiple KnapSac services can be configured to run concurrently in situations where multiple OpenVMS computers are sending files to the Windows computer or where files from different users need to be kept separate. KnapSac Service Control Program The KnapSac Service Control program is a GUI program which makes it easy to configure and control KnapSac services on the Windows computer. The Service Control Program provides configuration and control actions such as: Add a new service description Modify a service description Register and start a service Stop a service Display a service log file Remove a service from Windows