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Thread: Corrupted Indexes frequently

  1. #1
    Member B.B.Bongers's Avatar
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    Ing./BICT Brendo Bongers
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    Default Corrupted Indexes frequently

    Hi everyone,

    Our multi-user(80 users) application, builded with Alpha 5 has very, very often corrupted indexes. The big problem is that they occur at any moment so it's verry hard to reproduce a corrupted index in a test enviroment.

    I'd like to know what is really causing these corrupted index.
    By tracking down the cause I can solve the problem.

    Does anyone has a clue? Or does anyone has similar problems?
    And defiantly most important, how to solve/prevent/troubleshoot them.
    Maybe there is sort of tracetool/technique available like mssql server has.

    Thanks in advance,

    Brendo
    Ing./bict Brendo Bongers
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  2. #2
    "Certified" Alphaholic Stan Mathews's Avatar
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    Default Re: Corrupted Indexes frequently

    Quote Originally Posted by B.B.Bongers
    Hi everyone,

    Our multi-user(80 users) application, builded with Alpha 5 has very, very often corrupted indexes. The big problem is that they occur at any moment so it's verry hard to reproduce a corrupted index in a test enviroment.

    I'd like to know what is really causing these corrupted index.
    By tracking down the cause I can solve the problem.

    Does anyone has a clue? Or does anyone has similar problems?
    And defiantly most important, how to solve/prevent/troubleshoot them.
    Maybe there is sort of tracetool/technique available like mssql server has.

    Thanks in advance,

    Brendo
    Frequently discussed, check the similar threads at the bottom of this page or search.

  3. #3
    "Certified" Alphaholic
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    Default Re: Corrupted Indexes frequently

    Depending upon which operating systems are deployed you might check to verify that opportunistic locking has been disabled on all machines, including especially the machine acting as server.

    Are the problems occuring with "filtered" indexes?
    ... with "unique" indexes?

    -- tom

  4. #4
    Member B.B.Bongers's Avatar
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    Default Re: Corrupted Indexes frequently

    Quote Originally Posted by Stan Mathews
    Frequently discussed, check the similar threads at the bottom of this page or search.
    Thanks Stan, but with more than 240 tables and with a "lot" of users these mentioned suggestions/solutions are too vague.
    There most be a better effective methodology to pinpoint the cause.(like tracing). Where to look, which action did cause it, which table, which set etcetra.
    Ing./bict Brendo Bongers
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    http://www.brendobongers.nl

    "There's more than one way to skin a cat."

  5. #5
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    Default Re: Corrupted Indexes frequently

    do you have any indexes on numeric fields, and are the fields longer than 10 digits?

    if so, a somewhat interesting tidbit, if you use expressions anywhere as in scripts, if the length of the numeric field is greater than 10, and you want to reference the numeric field as a string, you can't say str(numericfield)

    say the field is 12 digits

    say str(numericfield,12,0) or str(numericfield,12,2)

    otherwise it returns unrecognizable values

    my own experience with "corrupted" indexes is that it always turns out to be a subtle problm with my code and/or especially having given Alpha a filter or query that cannot be resolved which will drop an index. Also, the more users you have the simpler you have to make things - like not using filters in indexes or sets. Better to handle the filtering/ordering directly that via indexes or set definitions.
    Last edited by martinwcole; 08-01-2006 at 10:42 PM.

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    Default Re: Corrupted Indexes frequently

    We struggled with index corruptions for a long time and only solved the problem by a series of design changes effected over a period of about a year. We still have index corruptions occasionally but nothing remotely like before the redesign.

    Our application is large with many sites installed but none would ever have reached 80 simultaneous users. Our largest sites currently would be in the range of 20 to 40 concurrent users.

    We were never able to come up with method for tracking down the root cause. There were probably several causes. Our design changes were based on having users leave their screens "as was" when the error occurred and we noted the areas where the errors occurred.

    Not surprisingly the errors occurred most often in those parts of the application where the users spent most of their time. As a result we focused on (1) reducing the number of indexes attached to any one table (and removal of filtered indexes), (2) set design simplification and (3) form redesign that ultimately helped enormously.
    Finian

  7. #7
    Member B.B.Bongers's Avatar
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    Default Re: Corrupted Indexes frequently

    Thanks for the suggestions so far.
    It will be I time consuming process to look at all tables and sets.
    Maybe Alpha will developed in the future a tool to measure the state of database/extended alpha/dbf files.

    I.e.
    - How often is a particular table queried.
    - Which queries are abnormally slow.
    - Which index is never used?
    - Which key will be a candidate to index?

    Critical business applications can't live without it.
    Last edited by B.B.Bongers; 08-04-2006 at 04:20 PM.
    Ing./bict Brendo Bongers
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    "Certified" Alphaholic Marcel Kollenaar's Avatar
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    Default Re: Corrupted Indexes frequently

    Brendo,

    Maybe not what you're asking for but you can do some profiling.

    Code:
    PROFILER_BEGIN()....PROFILER_END()
    Marcel

    I hear and I forget. I see and I remember. I do and I understand.
    ---- Confusius ----

  9. #9
    Member B.B.Bongers's Avatar
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    Default Re: Corrupted Indexes frequently

    Hi Marcel,

    We are going to trace users that are reporting open indexes.
    Maybe we could find some patterns in the tracelog.
    Ing./bict Brendo Bongers
    Software Engineer

    http://www.brendobongers.nl

    "There's more than one way to skin a cat."

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