Oh, my head hurts.
Haven't seen this before.

TSM server AIX 5.5.2 with no disk pool.
Clients back up to a VTL (which is an EMC CDL)
The VTL migrates to an LTO tape pool.

So the data flow is
clients => CDLPOOL => TAPEPOOL

CDLPOOL has MIGPROCESS=4

MIGRATE STGPOOL CDLPOOL  kicks of 4 migration processes, as one would
expect.

Except 3 of the processes choose a CDLPOOL volume as the input volume, and
an LTO2 TAPEPOOL volume as the output volume.
The 4th process chooses a CDLPOOL volume as the input volume, AND chooses a
CDLPOOL volume as the OUTPUT volume.

WHAT circumstance causes migration to choose an output volume in the SAME
POOL as the input volume?
.

W