Re: Risk in using sequence number?

You can also use DBMS_UTILITY.GET_TIME() to return 1/100ths of a second for more granularity.

Daniel Morgan

Keith Boulton wrote:

> 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 - 15:48:17 CST