Correction: I think I got the name of the first example wrong. It might be
BLOCKTAP not BLOCKIO.

/Tom Kern


On Thu, 26 Jun 2008 11:48:35 -0500, Thomas Kern <[EMAIL PROTECTED]> wrote:

>For programs inside a virtual machine that use standard CMS TAPEIO macros
>for their I/O, you can create a nucleus extension that intercepts the tape
>I/O and transforms it in some way. Two examples are the BLOCKIO program that
>was used by lots of installations to increase the real blocksize of data on
>tape from the 4K level of VMFPLC2 (before it was enhanced for larger
>blksizes), and a tape encryption product that called VM/Encrypt-Tape from
>VSoft Software (http://www.vsoft-software.com/products.html).
>
>In your new nucleus extenstion, you could direct that tape I/O to a CMS file
>on one of that user's minidisks or via IUCV to some central server for
>storage on it minidisks. The actual data packets could be compressed by the
>nucleus extenstion or in the central server if that is how you want to
>create your Virtual Tape System.
>
>Intercepting CP's I/O (like SPXTAPE) or SSCH I/O (like DDR) would not be
>feasible. but there are ways of not using those programs.
>
>/Tom Kern
>/U.S. Dept of Energy
>/301-903-2211

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