RE: DB2

["Joe Pluta" <joepluta@xxxxxxxxxxxxxxxxx>]

> From: Chris Bipes
>
> Yes but that is maintained by the DBM, called RRN.  So the rule is not
> broken.

I'm not going to spend a lot of time splitting hairs here, because what
we're debating is Dr. Codd's opinion, anyway.  But his words are:

"Each and every datum (atomic value) in a relational database is guaranteed
to be logically accessible by resorting to a combination of table name,
primary key value, and column name."

Forgive me if I'm misspeaking here, but as far as I can tell, the relative
record number is not considered a primary key, mostly because it's not part
of the actual data in the record.  Simply removing deleted records, for
instance with a RGZPFM, will change the RRN for a record, thereby changing
its "primary key".

AFAIK, databases that used RRNs for linkage were known as "network
databases" and while very fast, were susceptible to being completely
corrupted if a file got reorganized.

Joe