-----Original Message----- From: IBM Mainframe Discussion List [mailto:ibm-m...@bama.ua.edu] On Behalf Of Tom Marchant Sent: Wednesday, January 21, 2009 12:46 PM To: IBM-MAIN@bama.ua.edu Subject: Re: GDG Question
On Wed, 21 Jan 2009 13:22:42 -0500, Gerhard Postpischil wrote: >Tom Marchant wrote: >> I spent a *lot* of time in the microfiche, reading the CVOL code. Whatever >> the reason was for concatenating the generation data sets in reverse order, >> I don't think it was for performance. > >The names were stored in the catalog in inverse order (the >"nnnn" portion was complemented; i.e. C'0123' became >X'0F0E0D0C'). This placed the entries with latest generation >first, and explains why it was easiest to retrieve them in that >sequence. Yes, I'd forgotten that detail. Still, it begs the question, *why* was it stored that way? I suspect that it was a design decision to simplify the retrieval of the data sets in reverse order. I don't think that either forward or reverse order would offer a significant performance advantage. <SNIP> I have an idea: DSN=A.B.C(0) and DSN=A.B.C(-1) Probably the two most used forms of access for GDS entries. Regards, Steve Thompson -- Opinions expressed by poster may not represent poster's employer's views. -- ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
