The COBOL Editor's library option enables you to have multiple files open; each file is contained in its own sub-window. If you choose to back up a file in a window, you must close that file's window (using Esc), before attempting to load the backup. If you do not, you will receive a file-locked error. For details on how to back up files in multiple windows, see the section "Saving a File" in the chapter "Editor" in your Utilities Guide.