A process-permanent file is a file open for the life of the process. Any file open with the OPEN command, whether from level 0 of DCL or from a command procedure, stays open for the life of the process until explicitly closed with the CLOSE command. Default process permanent files inlcude:
Process-permanent files are stored in a special area in memory. Note that if you keep a large number of files open at the same time, you can exhaust this area. If this occurs, close some of the files (or log out).