Re: Risk in using sequence number?

Sybrand Bakker <postbus_at_sybrandb.demon.nl> wrote in message news:3koa7u0fh6uhhs69c1n14glq9cqg1716r7_at_4ax.com...
> On Thu, 21 Feb 2002 13:18:25 -0700, "Leigh Gold" <intan_5ee_at_yahoo.com>
> wrote:
>
> >What is the risk involved in using sequence number to keep track of the
last
> >record in a table?
> >
> >We use a table to keep history of an event, everytime an event changes,
we
> >insert a row in this history table with a sequence number as its primary
key
> >and information about this event. We are basing our query on
max(sequence)
> >to track the last time this event occurred. For some reason, the
developer
> >refuses to use sysdate for this purpose.
> >
> >Is there any risk involved in using the method?
> >
> >Thanks,
> >
> >Leigh
> >
> >
> >
> Loosing sequence numbers is inevitable using the cache option (which
> is the default) I'm not sure this won't happen with the nocache
> option. However, I never use that as the sequence number is supposed
> to be meaningless, and your sequence number should be meaningful.
> Probably hiring a different developer will be cheaper in the long run.
>

Except that the current developer is right - dates are precise only to the second and it is very easy to generate more than 1 event per second.

The use of sequences for this purpose is reasonable, I believe, given only that OPS is not used since multiple instances of the sequence exist so the allocation of sequence numbers does not occur sequentially (eh?). You also have to ensure that the sequence will never wrap. Received on Thu Feb 21 2002 - 15:20:30 CST