Hi, Richard.
The CDTAPE application that CA uses to distribute their products isn't a
true virtual tape sort of thing. It's just a way to package TAPE and
VMFPLC22 DUMP files onto a CD and be able to easy read them back on VM
without requiring a tape drive be attached to the VM system.
CDTAPE consists of two parts:
1) a CMS part that installs itself as a CMS nucleus extension and
intercepts TAPE and VMFPLC2 commands. It communicates via a socket
connection to the second part....
2) a PC application, written in Java, I believe, that does the actual
reading of the data on the CD. Based on the tape-like commands sent from
the CMS side, it read the required data blocks and sends them back to
the requester, where they are handed over to the TAPE or VMFPLC2
application for final processing and writing to disk.
There's nothing in the CDTAPE application that I am aware of that allows
for writing of CD tape files, only the reading of them.
DJ
Schuh, Richard wrote:
The problem is that SPXTAPE does not run as a normal application,
reading spool data and writing data to its output device using SSCH
logic. If there were normal virtual I/O operations writing to the
output (backup) or reading from the input (load), then the problem
has already been solved in a number of ways. CMS flat files could be
used, tape (either real or virtual) could be used, etc.
Virtual Tapes for VM are not something new. They have been in use in
the ACP/TPF world at least since late 1984. We even used them for an
MVS3.8 guest in 1984.
I do not know for sure whether CA's CDTAPE is a proper inclusion in
this discussion. I do not believe that it really does tape
virtualization. How about it someone from CA, is it a generalized
tape emulator or simply a specialized program that does not fit the
discussion?
Regards, Richard Schuh
