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Thread: The effect of a set on bandwidth

  1. #1
    Member
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    Tom Lyon
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    Default The effect of a set on bandwidth

    Over the past months, I have had some problems with index corruption which required all workstations to be shut down for rebuilding indexes. As a result, I decided to try to minimize the number of indexes. That helped a great deal, but did not eliminate the problem entirely. I then came up with this idea - eliminate the set relationship which I had defined. Instead of a set, I decided to use LQO to create queries on the individual workstations whenever I needed to show 'linked' data. The time required seems minimal and very acceptable. That worked well, but the impact was much more far-reaching that I anticipated. We track daily, weekly and monthly bandwidth usage on all servers. I began to see the real impact of eliminating the set relationship. Additionally, the entire database began to be much more responsive overall..I even eliminated Network Optimization on a whim. The database performance was still very satisfactory.

    I'm not sure what this all means, but I thought it significant enough to post. I have included attachments of the bandwidth monitoring graphs which indicated the bandwidth usage on the Alpha Five server. I instituted the change on a Saturday (a business day for us).

    I'd be interested to hear if others have encountered other solutions/improvements/etc. along these lines.

  2. #2
    "Certified" Alphaholic Stan Mathews's Avatar
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    Stan Mathews
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    Default RE: The effect of a set on bandwidth

    Tom,

    You don't mention your current Alpha version. I can't comment on your bandwidth observationsw, but since converting to 4.5 our index rebuilds are nil. We have, almost, forgotten the problem of disappearing index tags and such problems.

  3. #3
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    Tom Lyon
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    Default RE: The effect of a set on bandwidth

    I'm still at 4.03. I wanted to wait until 5.0 to upgrade, and yes, I know 4.5 addresses index corruption. However, the issue became a matter of basic database design when the set was eliminated. I will certainly be trying the set thing once I have 5.0 in my hands.

    Tom Lyon

  4. #4
    VAR csda1's Avatar
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    Ira J Perlow
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    Default RE: The effect of a set on bandwidth

    Tom,

    As I've stated many times before, the most important resource not to squander is the bandwidth of your network. Any time you apply a filter that does not completely use LQO, it forces A5 to read records to apply the filter expression. This is a big overhead, as you then have to run them all the time (assuming the database is constantly being changed) to refresh them.

    Not using sets is another example of being penny-wise and pound foolish. The speed of access for an A5 set is much lower than building the relationship through another A5 method. The set definition should not have more links than are required for the need. E.g. a report may only need 1 or 2 links, a form may require different links. Create as many sets as the demand requires.

    Index overhead is relatively small, so try to use them. Others may argue that more indexes slow a system down (certainly if you rebuild the indexes), but I have never seen this to be true during regular operation, and if the need is used often enough, is much better than a query.

    Regards,

    Ira J. Perlow
    Computer Systems Design & Associates
    csda@mediaone.net

  5. #5
    Member
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    Tom Lyon
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    Default RE: The effect of a set on bandwidth

    Ira said:
    -----------------
    Not using sets is another example of being penny-wise and pound foolish. The speed of access for an A5 set is much lower than building the relationship through another A5 method. The set definition should not have more links than are required for the need. E.g. a report may only need 1 or 2 links, a form may require different links. Create as many sets as the demand requires.
    -----------------

    Yes, I used to think that :) That's why I indicated that I had trimmed the set and indexes down to the bare minimum and simplified as much as I possibly could without affecting operations before trying to operate without a set.

    Still, the database performance without using sets is phenomenal, even taking "The speed of access for an A5 set is much lower than building the relationship through another A5 method" into account.

    That's not to say I understand how to design a database :) I usually use trial and error to determine what will work best based upon my understanding of the software at hand.

    Tom Lyon

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