Arnaud,
        One point that may have been missed is not all jobs can be preempted.  
From
the manual:
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The following are high priority operations that can preempt operations for a
The following are high priority operations that can preempt operations for a
mount point:
Backup database
Restore
Retrieve
HSM recall
Export
Import

The following lists operations that can be preempted and are listed in order
of priority. The server selects the lowest priority operation to preempt,
for example reclamation.
Move data
Migration from disk to sequential media
Backup, archive, or HSM migration
Migration from sequential media to sequential media
Reclamation
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Note that things in the top list will preempt things in the bottom list.
Note that things in the top list will preempt things in the bottom list.
The bottom list shows you in what order the preemption would happen.  Or if
those jobs in the bottom were running at the same time which one would get
the boot.

Note that the jobs in the bottom don't preempt anything.  So even though
Move Data has a higher priority that Reclamation it won't preempt a
reclamation job in order to run.  However, if a restore comes along and all
drives are used by move data's and reclamations then a reclamation job would
get the boot.

Kyle