Brian,

Your statement "The DBDELETE'd entry is no longer accessible." is not
100% true.

At a previous site we had a PM program that would read down the delete
chain looking for entries that matched a user specified criteria. Each
entry was displayed and you were given the option to print it, undelete
it or really delete it (alpha's set to spaces and numeric's set to
zero).

regards, 
  
Robert W.Mills 
Systems Development Manager 
Pinnacle Arvato 
(020) 8309 3604 


-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On
Behalf Of Brian Donaldson
Sent: 29 November 2006 04:41
To: [log in to unmask]
Subject: [HP3000-L] Adager question

I had to go and do some research on TurboIMAGE again just to refresh my
memory before I go throwing in my 0.5 cents worth on this topic --
 
Image detail sets:
 
There is no such thing as a "logical delete" or "logical delete flag." 
When a program calls DBDELETE on a *detail* dataset the BACKWARD and
FORWARD entry pointers of the previous and next entry on the chain no
longer point to the DBDELETE'd detail entry. The DBDELETE'd entry is no
longer  accessible. 
This DBDELETE'd entry then becomes part of the delete  chain.
 
If the detail dataset employs sort keys then the updating of the
backward and forward pointers gets even nastier. TurboIMAGE effectively
"breaks" the chain to rebuild the backward and forward entry pointers on
the chain........
 
 
If you DBDELETE entries from a manual master dataset and said
DBDELETE'd entry is part of a synonym chain then that entry is
supplanted  with the next entry on the synonym chain. For example, if
there are 6  entries on a synonym chain and you DBDELETE entry #3, then
entry #4 moves up to entry #3, entry #5 moves up to entry #4, entry #6
moves up to entry #5.
 
 
Just my 0.5 cents worth of what I know of TurboIMAGE.
 
 
Brian Donaldson.

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