HEDRICK@RUTGERS.ARPA (03/11/84)
From: Charles Hedrick <HEDRICK@RUTGERS.ARPA> Don't knock IBM systems in areas for which they are intended. They may not have EMACS, but IBM has put in more thought and had more experience with data processing than the Unix world. I don't know the context of this comment, but if somebody is proposing a command to request the operator to mount a tape, most of the parameters mentioned are good ones: - vol_ser: Now and then people do make mistakes. One of the major motivations for implementing labelled tape processing on Tops-20 was so the system could automatically verify that the right tape had been mounted. It is easy enough to mount the right tape on the wrong drive, or to get a couple of characters reversed and mount the wrong tape. This can result in overwriting critical data. Some of this is silly on a 4-user system that sits in the same room as the user terminals. But on larger Unix timesharing systems, there are the same operational requirements as for as IBM mainframe or a DEC-20. My all means, tell the system what tape you want mounted, so it can check. The assumption is that vol_ser is a volume identifier that occurs in machine-readable form at the beginning of the tape in a tape level. This switch should allow a list of volume identifiers, so that the system can switch automatically at the end of a reel. - file name: this seems a bit odd to me, but I didn't read the original proposal, so I don't know what it means. - mode: it sort of helps to tell the operator whether to put in a write ring - density: this may not be needed for read, but for writing, it is helpful to know at what density the user would like the label written. Of course these files (except for VOL_SER) should have default values. In addition, Tops-20 has a couple of other useful options: - remark: a quoted string to identify the tape to a human, for sites that don't good enough tape management that the VOL_SER is enough. /REMARK:"Look on the top shelf of cabinet 1" - protection: if you implement labelled tapes, specifies a byte that controls who can mount it. - label-type: if you mount a tape for writing, says what kind of label to write on it, in case the system supports more than one kind. (Tops-20 supports vanilla ANSI, and a form called TOPS-20, which implements some extra fields that will be meaningful only to other Tops-20 sites. We can also write EBCDIC labels, although we can't put any data on a tape labelled this way. Well, it's easier to initialize tapes for our IBM system using the 20.) -------