Range for user-defined SQLSTATE codes

I can't be the first person (or even the 10,000th) to want to define my
own SQLSTATE codes when raising errors in a stored procedure. I've
just tested doing so in a PL/pgSQL function access via JDBC, and I had
no problem retrieving the non-standard state from the SQLException. (I
used 'WWWWW' and 'ZZZZZ' as my tests.)

Is there anything like a standard range -- formal or otherwise -- for
such codes? A best practice? A general consensus? A half-painted
bike shed?

Thanks!

--
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Ian Pilcher arequipeno(at)gmail(dot)com
Sometimes there's nothing left to do but crash and burn...or die trying.
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