The practice of using an auto-created serial number as a unique record number for each record is one of those things I have always taken for granted.

Being a systems administrator and not a database designer, I am finding it difficult to explain in basic terms to a new database designer why EVERY database should have a unique record number. The FileMaker Bible claims they are great for invoicing, and I know I have databases that rely on them for filling in fields via relationships, but I know there is a 1 - 2 sentence explanation on why it is ALWAYS a good practice.

Can anyone help me out here?

While serial numbers are not unique or persistent (unliked Record ID's) they are extremely useful for generating primary keys to build relational file structures in FMP. In fact, auto enter serial number is the only way positively to guarantee unique values in a multi-user environment. In FMP 5.5 there are two new functions, one to get the next serial number, and the other to reset the serial counter to some value.

HTH

Old Advance Man