Hello list,

We have A VM that has DASD attached on 4 paths. The hardware is connected on
ESCON Directors. Last week one of the cables was plugged into the wrong
director. Channels 10-12 were connected to director2, channel 13 was
connected to director 1. It is obvious that this will address a different DASD.

Yesterday we used DDR to restore a tape to DASD.

<snip>
OUTPUT 3312 DASD SU3312
<snip>

When we started the copy DDR responded with: Volume Read : VM2076, etc. We
aborted the DDR and did a query of 3312, it responded SU3312. So we
suspected something wrong here and stopped to investigate. However, this was
the second DDR restore. The first one should have been restored to 3311 but
in fact the data was placed on a different disk. The DDR did not report a
wrong dasd label. It looks like DDR queried the label, accepted the label
and started writing the data to DASD. But on a different channel and in this
case on a different disk.

Now there is a discussion on how DDR and/or DASD IO will work in VM.

If an IO is executed in VM, is it always on the same channel?
Does DDR read the label and then write on the same channel?
Does DDR read the label before it writes a block of data or does it read the
label only once?

Regards, Berry.

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