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How to use Log Miner to verify filtered Oracle NULL columns

Learn how to use Log Miner to verify filtered Oracle NULL columns in an INSERT statement from a redo log write in this tip from Oracle database expert Brian Peasland.

Regarding redo log writes, does Oracle filter out all null columns for an INSERT statement and just write the minimal...

set of columns that have data to the redo log even when a column is explicitly set to null? I ask this because we are seeing an order of magnitude log writing over increasing size of the database when most of the activity is inserting.

Yes, Oracle does filter out the NULL columns in an INSERT statement. To verify, one needs to run Log Miner to mine some INSERT commands from the archived redo logs. If you do that, you will see that Oracle will have transformed your INSERT statement into one that specifically denotes the columns receiving the new values.

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This was last published in February 2010

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