Alan, shared tapes may have a problem under VM. I know they do when running
in an LPAR (see the disclaimer on the IBM under "restrictions" at
http://www10.software.ibm.com/developerworks/opensource/linux390/index.shtml

). The assign/unassign function is not implemented the same way in Linux as
in other OS.

- For MVS, the drive assign latch is set from vary online to vary offline.
- For VM, the drive assign latch is set from attach to detach (for tapes
single tapes)
- In LPAR mode, for SLES7 - the assign latch is not set at all so several
lpars can send commands to the tape at the same time!
- In LPAR mode, for SLES8 - the assign latch is only set during the time
from OPEN to CLOSE of the file. After the file is closed by one LPAR, it
can be stolen by another LPAR.

So I would guess that assign ... muiltiuser would have the same problems as
an LPAR.

The latch should be set from the INSMOD to the DELMOD, but it is NOT, hence
the strong recommendations for 2.2.16, and both streams of 2.4 NOT to use
shared tapes.

The CP attach multiuser sounds like it relies on the hardware
assign/unassign and you could find yourself with two EC's using the tape at
the same time under Linux.

We have verified that, in LPAR mode, the assign happening as I described.
Correct me if I am wrong if VM assign ... multipath uses a different
mechanism.

Regards, Jim
Linux S/390-zSeries Support, SEEL, IBM Silicon Valley Labs
t/l 543-4021, 408-463-4021, [EMAIL PROTECTED]
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