On Thu, Dec 18, 2014 at 8:36 AM, Chase, John <jch...@ussco.com> wrote:
> > -----Original Message----- > > From: IBM Mainframe Discussion List On Behalf Of Jon Butler > > Sent: Thursday, December 18, 2014 8:19 AM > > > > I'd like to state that even after 30 years of MVS, I still use the term > "file" when referring to > > mainframe datasets. In fact, if you look at the IBM COBOL manual, you > will see "File Organization", > > not "Dataset Organization"; PL/I refers to "FILE Attributes", etc. And > I think I can safely say I > > have never seen a DD NULLDATASET command ;-)) > > > > Don't be too hard on people just trying to learn. > > Q: What's the "structural difference" between a DB2 Table and a VSAM KSDS? > > A: The DB2 Table contains "rows" and "columns". The VSAM KSDS contains > "records" and "fields". > Hum, I might go a bit further. A VSAM KSDS is a disk data set which contains "records". A KSDS does not contain "fields" known to the access method. Therefore a VSAM KSDS does not have any "fields" in it. The "fields" within a KSDS record are imposed by the program reading the data set by overlaying the buffer contain the record with a template (COBOL FD or equivalent). VSAM itself does not know anything about them. At most, VSAM knows the location and length of the key data. This key data could be a single field or a composite of multiple fields in some application. BTW, have you been reading some of Joe Celko's SQL books? That, in general, is one thing he is constantly emphasizing about the difference between "files" (he doesn't use "data set") and "databases". As he keeps drumming: A table IS NOT a file! A "row" is not a "record". And a "column" is not a "field". > > -jc- > -- While a transcendent vocabulary is laudable, one must be eternally careful so that the calculated objective of communication does not become ensconced in obscurity. In other words, eschew obfuscation. 111,111,111 x 111,111,111 = 12,345,678,987,654,321 Maranatha! <>< John McKown ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@listserv.ua.edu with the message: INFO IBM-MAIN
