Fidel Viegas wrote:

> Hi again,
>
> I have created a single user POS just to show the client how it is
> going to work, and the requirements for it are the following:
>
> 1) The Invoice numbers have to be sequential, and no gaps are allowed
> 2) There shall not exist a case where invoice2.timesaved >
> invoice1.timesaved and invoice1.no > invoice2.no
>
> In the demo I have created, this is no problem. If the transaction
> fails, then I can always move the sequence back a number using
> ALTER SEQUENCE SEQ_NAME RESTART WITH GEN_ID(SEQ_NAME, 0)-1. Now, on
> the concurrent version, that will, obviously, not work. I could use
> locking, but I don't think that is the best approach.
>
> Can someone suggest a good approach to solve this?
>
> Thanks in advance,
>
> Fidel.

There is a technical paper on this.
Read "An Auditable Series of Numbers":
http://www.ibobjects.com/TechInfo.html#ti_AuditableSeries

Uwe