At 6:17 PM -0500 1/21/03, Brian Duncombe wrote:

>At 03:22 PM 1/21/2003 -0700, F. Alfredo Rego wrote:

...

>>With the benefit of these timely reminders, I would also like to update
>>my original post:
>>
>>>  > This is a question for the shadowing folks, having to do with
>>>  > performance (most likely).
>>
>>In addition to "performance", please include the comments from my two
>>colleagues.
>>
>>>  > "Depending on absolute entry numbers" can
>>>>  be one of the prices that they choose to pay to obtain performance.
>>
>>Given the issues mentioned by my two colleagues, the shadowing folks did
>>NOT have any other choice.  They HAD to depend on absolute entry numbers.
>>
>>>  > If such is the case, then it is certainly not possible to keep the
>>>>  master and the shadow repacked under different path criteria, because
>>>>  that would confuse the shadowing software's dependence on absolute
>>>>  entry numbers.
>
>Our Backchat product will support this, I assumed that everyone else would
>also.

Sigh of relief...  So, with a bit of extra effort, my theoretical
hunches can indeed be implemented by database-shadowing software :-)


>The problem, in our case, is that when we do a check for a matching
>"before" record and find a difference, then we go to our cross reference
>database that we maintain to see if that relative record has an xref
>entry.  This obviously involves more overhead

So, Brian's Backchat database-shadowing product chooses to pay the
price (extra overhead) to NOT depend on absolute entry numbers.


>but it has always impressed
>me how well it actually does work.  Hard to beat TurboImage.

I am certainly glad to see Brian's good news.  This is what I would
have hoped (and expected) from a purely mathematical analysis of
IMAGE's data structures.


>>This is so under any circumstances, regardless of the reason for the
>>dependence that shadowing software has on absolute entry numbers.

"Under any circumstances" now refers to the specific case of shadowing
software that depends on absolute entry numbers.  More general software
(such as Brian's Backchat database-shadowing product) is free to ignore
this restriction.  I will be able to sleep peacefully tonight.


>>The search for creative solution(s) to Eben's challenge continues!

Perhaps Brian and Even should have a chat about Backchat :-)

   _______________
  |               |
  |               |
  |            r  |  Alfredo                     [log in to unmask]
  |          e    |                           http://www.adager.com
  |        g      |  F. Alfredo Rego
  |      a        |  Manager, R & D Labs
  |    d          |  Adager Corporation
  |  A            |  Sun Valley, Idaho 83353-3000            U.S.A.
  |               |
  |_______________|

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