The Oracle (tm) Users' Co-Operative FAQ

How does Oracle handle updating a row that causes it to move from one partition to another ?


Author's name: Jonathan Lewis

Author's Email: Jonathan@jlcomp.demon.co.uk

Date written: 7th Mayy 2001

Oracle version(s): 8.1.7.0

In Oracle 8.1, the feature to allow an update to move a row from one partition to another appeared. How does Oracle handle such an update ?

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If you dump the contents of the undo segment or the log file after a simple update that moves a row from one partition to another you will find that Oracle takes three steps to handlethe task..

	Update the row in situ - which leaves it in the wrong partition
	Insert the corrected row into the correct partition
	Delete the row from the old partition

Clearly this is quite heavy on overheads (deletes are always expensive anuway as the whole row has to be written to the undo segment), so the feature should be used with care, and should probably not be used to move rows at a high rate.


Further reading: N/A


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