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Thread: Row chaining

  1. 05-05-2006, 02:14 AM #1
    malru
    malru is offline Member
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    Row chaining

    Hi,

    Please anyone explain me,what is row chaining & row migration?

    Thanks,
    Malru
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  2. 05-05-2006, 03:04 AM #2
    oracli
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    When a row is initially inserted into a table and the row is too large to fir in one data block, the row is "chained" in multiple blocks.
    When a row is already inserted in the bklock in it fits in it, but later it is updated and becomes bigger and does not fit any more in the block - the entire block is "migradted" to another block. The initial block contains a link to the migrated block so the initial rowid is not changed.
    Both of these occurences decrease I/O performance when reading these blocks.
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  3. 05-05-2006, 06:24 AM #3
    rgaskell
    rgaskell is offline Junior Member
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    Seems to me that you've posted a lot of threads in a short space of time asking questions, mostly about fairly basic DBA tasks. Have you tried searching the web first?
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  4. 05-05-2006, 06:37 AM #4
    davey23uk
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    rhetorical question if ever I saw one there
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