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November 2006, Week 4

HP3000-L@RAVEN.UTC.EDU

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From:
Brian Donaldson <[log in to unmask]>
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Date:
Tue, 28 Nov 2006 23:40:31 EST
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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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