Re: Why all the max length constraints?
Date: Mon, 29 May 2006 15:17:54 GMT
Message-ID: <CgEeg.4914$o%3.966_at_trndny07>
"dawn" <dawnwolthuis_at_gmail.com> wrote in message
news:1148773922.267863.170930_at_j55g2000cwa.googlegroups.com...
> [OK, here is my next "stupid question" as I cut a path in my study of
> the RM. Those teachers who just want to tell this student how ignorant
> she is are welcome to sit this out as I really am hoping to
> understand.]
>
> In SQL-DBMS's, like VSAM (and other indexed sequential files before
> them) a lot of attributes are specified with max length constraints.
> While there are some attributes where this constraint is related to a
> conceptual constraint (from the analysis phase), these lengths are
> often introduced for the logical model or implemenation in the DBMS.
Is VSAM really a DBMS? I looked up VSAM in wikipedia, and the definition I found suggests that VSAM is NOT a DBMS, although both IMS and DB2 are layered upon it.
In the world of DEC, which I know better, both Rdb/VMS and VAX DBMS were layered on KODA. KODA was not a DBMS but a useful building block.