SCN in the block ?
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Thread: SCN in the block ?

  1. #1
    Join Date
    Feb 2002
    Posts
    267
    Hi,
    Is SCN no also stamped in the header of
    the oracle data block., if so is there any way
    of seeing it.
    Regards
    sonia

  2. #2
    Join Date
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    Yes. the block header contains SCN no. for the block. I am not sure but I think dumping the block may show the SCN.

    Sanjay

  3. #3
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    You can see the SCN by dumping the block.
    e.g.
    Code:
    Oracle process number: 11
    Unix process pid: 4227, image: oraclefdbsd
    
    *** 2002-09-16 14:29:01.920
    *** SESSION ID:(8.868) 2002-09-16 14:29:01.919
    Start dump data blocks tsn: 4 file#: 5 minblk 1312 maxblk 1312
    buffer tsn: 4 rdba: 0x01400520 (5/1312)
    scn:0x0000.00193717 seq:0x03 flg:0x00 tail:0x37171003
           frmt:0x02 chkval:0x0000 type:0x10=DATA SEGMENT HEADER - UNLIMITED
     
      Extent Control Header
      -----------------------------------------------------------------
      Extent Header:: spare1: 0      tsn: 4      #extents: 11     #blocks: 1549  
                      last map rdba: 0x00000000  #maps: 0      offset: 4128  
          Highwater:: rdba: 0x014020ca  ext#: 10     blk#: 97     ext size: 520
    00193717 is the HEX value, convert it to decimal which is the SCN for the block.

    Sanjay

  4. #4
    Join Date
    Feb 2002
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    267
    thanx sanjay,
    Can u pls tell me who is responsible for updating the scn in the block and when it will be updated ? duing a checkpoint ?
    Regards
    sonia

  5. #5
    Join Date
    Feb 2002
    Posts
    267
    thanx sanjay,
    Can u pls tell me who is responsible for updating the scn in the block and when it will be updated ? duing a checkpoint ?
    Regards
    sonia

  6. #6
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    Whenever a transaction is commited a new SCN is issued I am not sure which process will right SCN to the data block.

    Sanjay

  7. #7
    Join Date
    Feb 2002
    Posts
    267
    Hi sanjay,
    U had told about dumping the block....
    How exactly to do that...
    regards
    sonia

  8. #8
    Join Date
    Feb 2000
    Location
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    From SVRMGR do this..

    ALTER SYSTEM DUMP DATAFILE FILE# BLOCK BLOCK#;

    One trace file will be generated in the UDUMP directory.

    Sanjay

  9. #9
    Join Date
    Aug 2002
    Posts
    21

    Wink

    I don't think there is anything like block scn scn is for datafile and on dumping the block u see the file scn only am i correct sonia/sanjay

  10. #10
    Join Date
    Mar 2002
    Posts
    200
    In my little knowledge, I know that SCNs are for Data File Headers, Control Files, Redo Logs and Rollback Segments. They are NOT for data blocks. CKPT archive process writes the SCNs to these files when a COMMIT is initiated.

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