Storage Optimization Question
David Grove asked whether dbexport and dbimport equals repack, shrink and defragment on every table (IDS 12.10.FC12). Art Kagel said defragment then repack with shrink comes close. Paul Watson said dbimport gives better results, as does ALTER FRAGMENT into a new space, since defrag/shrink does not move other fragments to make contiguous space. Martin Graney noted customers would resist the downtime.
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IDS 12.10.FC12
Solaris 10 1/13
Is doing a dbexport & dbimport of a database comparable to doing a repack, shrink, and defragment on every table?
Thank you.
David Grove
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David Grove
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#Informix
If you did a defragment, then repack with shrink it might be close to a complete reload. How close depends on how fragmented the free space is in the dbspace(s) holding the tables. Art Art S. Kagel, President and Principal Consultant ASK Database Management www.askdbmgt.com Blog: http://informix-myview.blogspot.com/ Disclaimer: Please keep in mind that my own opinions are my own opinions and do not reflect on the IIUG, nor any other organization with which I am associated either explicitly, implicitly, or by inference. Neither do those opinions reflect those of other individuals affiliated with any entity with which I am affiliated nor those of the entities themselves.
David:
Very good question! I would think yes but doing a dbexport and dbimport to defragment and shrink my customers' databases probably wouldn't go over to well with them.
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Best regards,
Martin Graney
Queues Enforth Development, Inc.
Stoneham, MA 02148
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Yes ish - the dbimport should give better results. Alter fragment into new-space should give you the same/similar results as the dbimport.
Defrag/shrink will not move other table fragments out of way to give to contiguous space - remember windows defrag ?
Cheers
Paul
Paul Watson
Oninit LLC
+1-913-387-7529
www.oninit.com
Oninit® is a registered trademark of Oninit LLC
Thank you, Martin. Yes, it doesn't generate a log of enthusiasm among users to schedule downtime! DG ------------------------------ David Grove ------------------------------
Paul, Thank you for your comment. There remains a lot about Informix that I have not mastered. Defrag/Repack/Shrink is certaiinly one of these areas. I thought that "shrink" moved all the data to the "front" and left as much space as possible at the "end". Or maybe that data movement is only within the extents that have already been allocated, and not general space management over the chunk as a whole?? DG ------------------------------ David Grove ------------------------------