KnapSac consists of a VMS Client and a Windows or Linux Server. The Client and Server communicate using TCP/IP. The Windows KnapSac Server runs as a Windows Service on Windows 2000, Windows 2003, or Windows XP. The Linux KnapSac Server runs as a deamon process.

The KnapSac commands to save or restore VMS files are entered on the VMS Client. (see KnapSac Examples)

When a KnapSac comand is entered on the VMS Client, the Client connects to the Windows or Linux Server using TCP. After the server accepts the connection, the Client and Server cooperate to save or restore the VMS files.

KnapSac commands can be set up in VMS batch command procedures to automate VMS to Windows/Linux backups.

KnapSac supports full disk image backups plus incremental and differential backups, as well as simple file mode backups. KnapSac includes data compression to minimize the network transfer time and the size of the backup files on disk.