Suggestions

I have a physical file that will hold gas type information, but one of the 
fields needs to be an integer id field.  My experience with other db formats 
is that I could set that field to auto generate so that as each record is 
written it will increment the count by 1.  we will be using this for cross 
referencing to some other files and must be unique.

I know I can read through the file and increment a counter, but that seems 
to have a huge overhead, not to mention that as time goes on, it'll take 
longer and longer to calculate.

Does anyone have a viable suggestion on how to accomplish this? 

Douglas