As you say, the DBGET mode 1 arg @ establishes a chain so-to-speak of master
entries in sorted sequence.  What's the difference twixt forward & backward
at this point?  Should be no difference - we've done nothing except
establish the chain, not our traversal direction.  So let's try both ways...

Forward...
DBFIND mode 1 arg @ set FLEET-MASTER
status = 0, record count = 10.
DBGET mode 5 set FLEET-MASTER
status = 0, buffer contains record with smallest key, works great.

Backward...
DBFIND mode 1 arg @ set FLEET-MASTER
status = 0, record count = 10.
DBGET mode 6 set FLEET-MASTER
status = 14.  IMHO I should get the record with the largest key, and after
reading all 10 of the records on the chain I should then get status = 14,
but not before traversing the chain, right?

TIA
Tracy

> -----Original Message-----
> From: Jerry Fochtman [mailto:[log in to unmask]]
> Sent: Tuesday, August 15, 2000 11:56 AM
> To: Tracy Pierce; [log in to unmask]
> Subject: Re: [HP3000-L] Image B-Trees on MPE/iX 5.5 pp 7
>
>
> So what doesn't make sense?  Sure, you can do a backward read of a
> KSAMXL file (FINDN/FREAD). The DBGet error 14 makes sense in that
> you've established a chain of all entries(DBFIND, key @), so when
> reading this list of sorted entries backwards, one should expect to
> get 'beginning of chain', likewise 'end of chain' (DBGet error 15)
> reading forward (DBGET(5)).  Keep in mind that the DBFIND, mode 1,
> qualifier @ essentially established a logical chain of all master
> entries in sorted order.  And trying to read backwards when you're
> already pointing to the beginning of the logical chain (DBFIND,
> DBGET(6)) can't go backwards, hence the beginning of the chain error.
>
>  From what you've described, there doesn't appear to be any problem
> with how it is operating.
>
>
>
> At 11:22 AM 8/15/00 -0700, Tracy Pierce wrote:
> >I'm trying to use Image B-Trees to gain sequential access to
> my Image Master
> >sets.  I've done
> >:DBUTIL
> > >> SET VMSDB BTREEMODE1=ON
> > >> ADDIndex VMSDB FLEET-MASTER
> > >> ADDI VMSDB ACT-TYPES
> >and have changed a couple of programs to use DBGET mode 5 &
> 6 (instead of 2
> >& 3), and have changed the corresponding 'rewind' (DBCLOSE
> mode 3) to a
> >DBFIND mode 1 arg @.
> >
> >This seems to work, at least partially:  Using FLEET-MASTER
> as an example,
> >the DBFIND always works, and despite no record pointers it
> reports all 10
> >records on the dataset.  DBGET mode 5 yields the first
> ("smallest") record;
> >subsequent DBGET mode 5's yield increasing key values.  Once
> I've done a
> >DBGET mode 5, a subsequent DBGET mode 6 goes backward (how??
>  backward read
> >in KSAMXL file???).  But DBGET mode 6 immediately after the
> DBFIND just gets
> >me status 14, beginning of chain.  Kind of makes sense, but
> not enough; Stan
> >says it should work.
> >
> >Are there patches I've overlooked or something?
> >
> >:version dbutil.pub.sys
> >VERSION  C.55.00 Copyright (C) Hewlett-Packard 1987.  All
> Rights Reserved.
> >
> >DBUTIL.PUB.SYS
> >
> >SOM #1
> >$Header: nrt0.s,v 1.12 87/06/08 09:36:52 cary Exp $
> >Compiled on WED, SEP 24, 1997, 10:31 AM
> >S35S391C.HP30391.TURBONM
> >Copyright (c) 1987  Allegro Consultants, Inc.
> >SPLash! 97E 4.19
> >
> >t   the prior written consent of the Hewlett-Packard Company.
> >his program except for archival purposes is prohibited withou
> >d   in a retrieval system. Copying or other reproduction of t
> >me  and shall not otherwise be recorded, transmitted or store
> >987 This program may be used with one computer system at a ti
> >Compiled on THU, JUN  6, 1996,  7:33 PM
> >REDO.MODULE.TURBONM
> >Copyright (c) 1987  Allegro Consultants, Inc.
> >SPLash! 96E 4.10
> >
> >K Tracy Pierce, Systems Programmer
> >Golden Gate Bridge, Hwy & Trnsp Dist
> >PO Box 9000, Presidio Station
> >San Francisco, CA  94129-0601
> >mailto:[log in to unmask]
> >415-923-2266
>