scn
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Thread: scn

  1. #1
    Join Date
    Jan 2008
    Posts
    31

    scn

    Hi,

    Just a strange change.
    No activity is going on (ofcourse oracle internal activities keep scn moving)

    The first query gives me same scn (always) but the reverse always gives one incremented......

    Any particular reason ??

    thx



    SQL> Select CURRENT_SCN from v$database
    2 union all
    3 Select dbms_flashback.get_system_change_number AS CURRENT_SCN from dual;

    CURRENT_SCN
    -----------
    514882
    514882

    SQL> Select dbms_flashback.get_system_change_number AS CURRENT_SCN from dual
    2 union all
    3 Select CURRENT_SCN from v$database;

    CURRENT_SCN
    -----------
    514890
    514891

  2. #2
    Join Date
    Apr 2006
    Posts
    377
    It would appear that the call to dbms_flashback is advancing the SCN:

    Code:
    SQL> Select CURRENT_SCN from v$database
      2   union all
      3  Select dbms_flashback.get_system_change_number AS CURRENT_SCN from dual
      4   union all
      5  Select current_scn from v$database;
    
    CURRENT_SCN
    -----------
         654231
         654231
         654232

  3. #3
    Join Date
    Jan 2008
    Posts
    31
    I was under the impression that only COMMIT will increase the SCN; But i guess there are so many other things which does this ?

    any thoughts about other actions which trigger the scn changes ?

    -sunil

  4. #4
    Join Date
    Apr 2006
    Posts
    377
    A SCN is a logical time stamp (Oracle's internal database clock) that defines a committed version of a database at a point in time. There are many things that can advance the SCN including scheduled jobs, Oracle Advanced Queueing, SMON, etc.

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