I will try to look into this further and will post an append if I
get more info, or have led you astray.

In regards to adsm assigning a private category that is true...but
by default it will be the same on both servers which will cause
problems.  You may be able to use different private categories on
the 2 adsm servers...but we can not guarantee that this configuration
will work...we have not tested this environment...greg

two related appends attached below...
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Re: your example, wouldn't the tape that is being used by the
first ADSM server no longer be in the "scratch" category as
defined by the 3494, and thus not eligible for use by the second
ADSM server?


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Greg - Thanks for your response on this.  One thing I don't understand is
       "RESERVE macro does not currently operate across systems".
From everything I learned from my MVS days, a Reserve is a physical hardware
latch state whose purpose is to (crudely) arbitrate access from multiple
systems.  That is, the host seeking exclusive access issues the system call
which causes the Reserve state and thus no other host can access the device.
This was quite visibily effective in S/370 devices.
    In 3590 programming in Unix, one issues an ioctl system call specifiying
SIOC_RESERVE.  If you get exclusive access, the call works; else some other
host has it, and the call fails, and you can wait for that host to do an
SIOC_RELEASE.  The device drivers manuals specifies these to be functions
for use "in a host-sharing environment".
    Reserves in general clearly work across systems: that's what they're for.
So I don't understand why ADSM could not be sure that it has exclusive rights
to a drive.  What am I missing?