Do you need guaranteed sequential or monotonic numbers?
If so, ignore this post. If unique is good enough, read on...
> Hi folks
> i am sure this has been discussed before if so please point me to the
> correct thread / message,
> Recently i came across a peculiar problem we have several transactions
> which required sequence number , now this number has to be generated and
> handed out fast enough!!! So it kind of rules out putting it in a db and
> accessing it!!!
Not if you grab bunches of sequence numbers at once, say 1000.
> So i hit upon a simple solution of putting a sequence number in a hash
> table and looking up the number whenever i required one!!
>
> The situation was okie with a few users but with a few more users it was no
> more thread safe!!! So i synchronised on the method...
>
> Now how do i do the following
> 1) Make it instance safe as more than one bean could be in my pool and
> they could do a update it and lead to dirty reads??
Would using entity beans avoid this problem?
> 2) How do i make sure it is cluster safe??
Each cluster grabs it's own bunches of numbers -- the DB synchronizes this.
> 3) How do i ensure even if the server goes down the last value of the
> transaction number gets saved in the db and i can start afresh from there
> on!!!
You save the last number when you grab the bunch. If you crash/shut down the
remaining numbers in the bunch just never get used.
> 4) I am trying to [not?] do a sequence number in Oracle a) becos it is
database
> specific
> b) the overhead and contention on it will be quite high!!
>
> Is there any other approach , please let me in how u folks go about it
> normally...
The above is what I do -- but I haven't done it with EJB's yet.
Tom
--
Tom Davies -- [EMAIL PROTECTED]
http://mwmbers.optushome.com.au/tomdavies
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