Uncommited data in datafiles ?
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Thread: Uncommited data in datafiles ?

  1. #1
    Join Date
    Feb 2002
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    267

    Uncommited data in datafiles ?

    hi,
    When an instance is up and running is there any situation
    where in uncommited data can be present in datafiles (Except when oracle is doing istance recover)

    Regards
    sonia

  2. #2
    Join Date
    Feb 2000
    Location
    Singapore
    Posts
    1,758
    Yes, uncommited data can be on datafiles.
    Sanjay G.
    Oracle Certified Professional 8i, 9i.

    "The degree of normality in a database is inversely proportional to that of its DBA"

  3. #3
    Join Date
    Feb 2002
    Posts
    267
    hi sanjay,

    can u explain me...in what situation..

  4. #4
    Join Date
    Jan 2001
    Posts
    2,828
    Hi sonia

    In many many situations..whenever dbwr is signalled to write dirty block to the database it just does that..and that dirty blocks will contain uncomitted data..now there are many conditions under which the dbwr flushes dirty buffers to disk and under these conditions dbwr will not check wheather the blocks contain comitted data or not it just flushes..

    regards
    Hrishy

  5. #5
    Join Date
    Mar 2002
    Posts
    200
    Originally posted by hrishy
    Hi sonia

    In many many situations..whenever dbwr is signalled to write dirty block to the database it just does that..and that dirty blocks will contain uncomitted data..now there are many conditions under which the dbwr flushes dirty buffers to disk and under these conditions dbwr will not check wheather the blocks contain comitted data or not it just flushes..

    regards
    Hrishy
    Hrishy is right. For instance, DBWR wakes up every three seconds and writes all the dirty buffers to the data files (in Oracle 8i).

    During instance recovery, SMON Rollsback all the uncommitted transactions.

  6. #6
    Join Date
    Nov 2002
    Location
    New Delhi, INDIA
    Posts
    1,796
    well you can try it your self...

    1. Create a small tablespace with 1M datafile(or what ever is the smallest possible for you);
    2. Alter the datafile of this tablespace to autoextend on;
    3. create a table in this tablespace and start inserting rows(say 80000 or more). Do not Commit;
    4. Watch your datafile grow with uncommited data.

    HTH
    Amar
    "There is a difference between knowing the path and walking the path."

    Amar's Blog  Get Firefox!

  7. #7
    Join Date
    Jan 2003
    Location
    india(bangalore )
    Posts
    14

    hello sonia

    yes uncommited data can be store in data files of the database . it is like this . when the dirty data buffer . is full .and there no free buffer space in the database buffer cache .and the checkpoint . indicate the dbwn to write the dirty to write in the datafile.
    abdulkhadeer

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