You know, it's funny, I've had this @Unique field in my supported apps for a long time and I just trusted it did what's implied. (kindof) A unique number for the database docs? How does it do that because the Help desciption is vague.
Without a parameter, returns a random, unique text value. With a parameter, removes duplicate values from a text list by returning only the first occurrence of each member of the list. One wonders: Unique to what?

I'm doing an enhancement to create some related docs in a separate database and I figure I'll use the same technique that my attachment database uses. I did some digging in Notes.net just for *hits and giggles to confirm my use of this and found this explanation :
@Unique uses part of the users name and a part that is generated based on the time. So as long as your unique numbers are generated by different users they will 99.9% be unique irrelevant whether you have access to it or not.
If your unique number is generated by an agent and therefore by one id and if you are generating alot you might run into trouble.
See this post from Andre Guirard (well the whole thread might be of interest to you):
Thanks Marjan and Andre