OK, this is old-style "blue skying". I've read a LOT recently about
backups of Linux DASD on z/OS using FDR or DFDSS "full volume" backups.
The main problem is that Linux caches DASD updates in memory and so the
DASD resident image may (likely is) incorrect.

Using Linux backup utilities is said by some to be "too slow" and
"network intensive" because many such do the backup on z/OS by sending
the data over IP.

Why not a combination? Have a daemon process on Linux. When the z/OS
backup process starts, it establishes an IP connection to this daemon.
The z/OS process then starts doing the backup by directly reading the
DASD. As I understand it, the "concurrent copy" hardware informs the
z/OS backup process of all tracks that are changed after it has backed
them up and the z/OS backup process then rereads those tracks. Is this
true? If so, then the only thing missing is the data which which is in
the cache which had not been commited to DASD since the start of the
z/OS backup process. When the z/OS backup process signals the Linux
daemon that it is about to finish, the Linux daemon sends only the
"dirty" data in the cache over TCP to z/OS.

I have no idea how to do anything about z/VM's MDC, if that is involved.
This also assumes that a each logical DASD volume under z/VM is a
physical DASD volume. The DASD would likely need to be CDL formatted as
well.

This is just an idea. It may well be too stupid to even refute. I'm not
a DASD backup specialist. If any vendor wants the idea, it is
free-as-in-beer.

--
John McKown
Senior Systems Programmer
UICI Insurance Center
Information Technology

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