Locally managed tablespaces
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Thread: Locally managed tablespaces

  1. #1
    Join Date
    Oct 2001
    Location
    India
    Posts
    36
    Dear friends,
    I need a help from u all. Right now i planning to use dictionary managed tablespaces, but so many documents says that LMT(locally managed tablespaces) is very good in performance and also in maintenance. I am convinced with that. I didn't understand one thing during my testing, I have create an LMT with 1m of uniform extent allocation, and at the table level i gave 5m as initial extent, when i queried dba_extents, it has taken 5 extents of 1m each, is this right even in case of initial extent also? will it not take the initial extent which is given at the table level?

    One more doubt, in earlier versions documents says that too many extents is performance drain, is it same in 8i also?
    Till how many extents i can plan for a table and how many are suggestable?
    See i have tables of size 60gb and 30 gb which will grow in a year, how can size this. please help me in this regard..

    Thanks in Advance.


  2. #2
    Join Date
    Nov 2000
    Location
    greenwich.ct.us
    Posts
    9,092
    Originally posted by V6163
    Dear friends,
    I need a help from u all. Right now i planning to use dictionary managed tablespaces, but so many documents says that LMT(locally managed tablespaces) is very good in performance and also in maintenance. I am convinced with that. I didn't understand one thing during my testing, I have create an LMT with 1m of uniform extent allocation, and at the table level i gave 5m as initial extent, when i queried dba_extents, it has taken 5 extents of 1m each, is this right even in case of initial extent also? will it not take the initial extent which is given at the table level?

    Yup, this is correct. When you setup an LMT with uniform extents, all the extents are the same size. Period.

    LMT's are all I use (except, of course, for SYSTEM tablespace).


    One more doubt, in earlier versions documents says that too many extents is performance drain, is it same in 8i also?

    In the old days, this was true. The number of extents was not really the issue, but how fragmented your tablesapce was. With LMT's this is not really a concern as the extents are all one size.


    Till how many extents i can plan for a table and how many are suggestable?
    See i have tables of size 60gb and 30 gb which will grow in a year, how can size this. please help me in this regard..
    I typically setup a couple tablespaces for each application; SMALL, MEDIUM, and LARGE. For each tablespace I assign an appropriate UNIFORM extent size and then assign my tables to their appropriate tablespace. When a table gets big enough to move to the next uniform extent size, I move it to another tablespace.
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  3. #3
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
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    3,938
    [[/B][/QUOTE]
    I typically setup a couple tablespaces for each application; SMALL, MEDIUM, and LARGE. For each tablespace I assign an appropriate UNIFORM extent size and then assign my tables to their appropriate tablespace. When a table gets big enough to move to the next uniform extent size, I move it to another tablespace. [/B][/QUOTE]

    I do exactly the same and this is what Oracle recommends.


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