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  1. #1
    Join Date
    Aug 2009
    Posts
    1

    Unanswered: What they actually are ? -- index levels

    I have these couple of Qs on DB2 LUW. Can anyone please give me the inner details -
    1. What does NLEVELS actually mean to the physical design (indexes) of the database?
    2. What role does NLEVELS play when the optimizer selects one access plan?

    Thanks & Regards,
    Pranab

  2. #2
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    You can do a google search on B-Tree indexes to understand what the tree looks like, and why there are levels. Obviously, a very large table may require an index tree to have more levels than a small table.

    The number of levels usually does not affect the access path selection, since on additional level requires only one addition page I/O, which may be in bufferpool memory already.
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

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