Where does the SCN resides (system change number)

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paparao

  • Oct 23rd, 2006
 

In Control file.

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venu9955

  • Dec 1st, 2006
 

Control file

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Rajendra Singh Chauhan

  • Dec 10th, 2006
 

in control files, datafile headers, and redo records,alert log file

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cbryll

  • Jan 23rd, 2007
 

online redo log files

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senthilora

  • Sep 24th, 2007
 

SCN - System Change Number - is always getting incremented by Oracle server and will be used to make sure the consistency across the database.


SCN number will be updated in almost all places of the database.


1. CONTROLFILE

2. DATAFILE HEADERS

3. REDOLOG FILES (and hence ARCHIVE LOG FILES)

4. DATA BLOCK HEADERS


But not in ALERT LOG file as it is not part of database. 

g.mrunalini

  • Feb 12th, 2008
 

SCN changes for every 3 minutes in 10g and for each and every action in 9i. It resides in control files and data files. CKPT (checkpoint) background process updates the SCN numbers from control files to the datafiles. SMON (system monitor) background process checks for the SCN numbers to be same in both datafiles and control files while starting the database. If same, then only the database is consistent. Otherwise, the database will not start.

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