PANIC killing vacuum process

Alls,

we have develop a script to execute the vacuum full on all tables of our
very big database , since it is a 24 x 7 available system we have not a
timeframe to exec the vacuum full.
so we try with this script running the vauum full table by table and if
the vacuum generate the waiting status for other connections we kill the
vacuum .
But we encounter following problem:
with kill command:

2010-11-03 14:25:27 CET [19324]: [4-1] FATAL: terminating connection
due to administrator command
2010-11-03 14:25:27 CET [19324]: [5-1] STATEMENT: vacuum full analyze
verbose tracking.as_history_status ;
2010-11-03 14:25:27 CET [19324]: [6-1] PANIC: cannot abort transaction
75073917, it was already committed

with pg_cancel_backend(pid) command:

CPU 0.18s/0.26u sec elapsed 3.79 sec.
ERROR: canceling statement due to user request
PANIC: cannot abort transaction 75081452, it was already committed
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!> quit
-> \q

the server crash and we have a service unavailiability on our production
system.

Is it possible to softly kill a vacuum process without risk a panic ?????

thanks a lot

Silvio Brandani
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