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Update of operating system timestamp of datafile

Posted on 2001-06-05
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When does the operating system timestamp of the Oracle datafile get updated ?  Normally, it is seen to happen at instance shutdown, but can it happen in between when the instance is running ?  Under what conditions ?

The OS timestamp does not change every time the DBWR process writes to the datafile in Windows NT - when does the timestamp actually change in a Windows NT environment ?
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Question by:Eileena
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by:fva
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When auto-increased?

F.
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ORACLEtune earned 50 total points
ID: 6156816
hi,

the Oracle8i Database "engine" has different moving parts,
oracle datafiles are updated after an Oracle8i CHECKPOINT occurs.  A CHECKPOINT is a database engine action whereby the SGA REDO_LOG buffer is written to an on-line redo.log.  This action is followed by a DBWR action whereby all "dirty-blocks" in the SGA DATA_BLOCK_BUFFER (i.e. cached/changed datablocks) are written to their respective oracle datafiles.  The Oracle SCN (System Change Number) is written to synchronize and map each database transaction to its repective REDO_LOG & oracle datafile & oracle control file.  This concurrency architecture allows Oracle to recover in event of instance, media, user, or other failure.

"When does the operating system timestamp of the Oracle datafile get updated ?"

- after a database DBWR operation occurs.  

This means the database transaction data buffered in the SGA has been written to disk.  Buffering data in the SGA, allows Oracle to write to disk every 30-45 minutes, this way your system is not i/o bound by constant database writes to disk.  Check your alert log, your CHECKPOINT switches should be occuring every 30-45 minutes in a tuned database engine.

see ya,
Eric
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by:misho2000
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I think that every time Oracle process writes to any database file OS timestamp is updated.
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