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What is the System Change Number? [message #241567] Wed, 30 May 2007 01:10 Go to next message
trantuananh24hg
Messages: 668
Registered: January 2007
Location: Ha Noi, Viet Nam
Senior Member
Dear all and especially Michel!

I am wondering about the SCN - System Change Number. I know it is a sequence number whenever Database is being opened reset log. But I don't know where is the view V$ to see it, and when does SCN occur?

Would you like to guide me, and send me a document (or link) to learn about it carefully?

Thank you very much!
Re: What is the System Change Number? [message #241580 is a reply to message #241567] Wed, 30 May 2007 01:40 Go to previous message
Michel Cadot
Messages: 64110
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
SQL> select current_scn from v$database;
         CURRENT_SCN
--------------------
       4339477155665

1 row selected.

SQL> select dbms_flashback.get_system_change_number from dual;
GET_SYSTEM_CHANGE_NUMBER
------------------------
           4339477155666

1 row selected.

Many things can change SCN mostly user and internal commits.
As you can see in my example, I was alone on my db but the time I typed the 2 statements SCN increased of 1.
SCN is just a tick (like clock tick) to measure db internal time (like clock measures "real" time).

Regards
Michel
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