Datafile Header
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Thread: Datafile Header

  1. #1
    Join Date
    Jul 2001
    Posts
    93
    Hi,


    I am wondering how much space will be allocated for a datafile header, also will this differ the way the tablespace is managed(Dictionary or Local).

    Thanks
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  2. #2
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
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    select FILE#, BYTES from V$DATAFILE_HEADER;
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  3. #3
    Join Date
    Oct 2000
    Posts
    467
    hi julian,
    That will not give you the header size of the datafile..but infact the whole size
    I really doubt if you could actually find the header size of the datafiles which could be OS dependent.
    Cheers
    Vinit
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  4. #4
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
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    3,938
    You are right. The query returns in fact the size of the datafile. I also doubt if you could find the header size of the datafiles. Who needs such an information :-)



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  5. #5
    Join Date
    Jul 2001
    Posts
    93
    Hi,

    I was doing some research and came across the file header size.

    Never mind i will try to find out..

    Thanks
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  6. #6
    Join Date
    Jun 2000
    Location
    Madrid, Spain
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    7,448
    if you have tablespace manager you can see that 2 blocks is reserved for the overhead, now I am not sure what happens if you have several datafiles, AFAIK they are still 2 blocks but I have only checked this with small tablespaces, may be someone else have tried with larger tablespaces?
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  7. #7
    Join Date
    Dec 2000
    Location
    Ljubljana, Slovenia
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    4,439
    In localy managed tablespaces file header is definitely larger than 2 blocks. For LMT file header includes a bitmap for extents, and this bitmap is allways 64K in size, regardless of the block size.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?
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