Page Verify = Checksum

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Page Verify = Checksum

Sporidium

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November 5, 2020 at 11:38 am

#3804557

Hi

I'm belated changing the page verification option for a database from NONE to CHECKSUM. I'm aware this only affects future writes to the database, and existing pages won't have that checksum calculated until they are updated or the relevant tables or indexes are rebuilt.

My question is: would an ALTER INDEX ... REORGANIZE also cause checksums to be calculated? If not, why not?

Thanks

Gary
December 22, 2020 at 6:23 am

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Grant Fritchey SSC Guru Points: 397721 More actions · Answer 1

I'd say that REORGANIZE is unlikely to because it touches so few pages normally when it changes indexes. A REBUILD on the other hand, that might do it. I only say "might" because I haven't tested it. I'm pretty sure, rebuilding all indexes, rewrites most of the pages in a database.

----------------------------------------------------The credit belongs to the man who is actually in the arena, whose face is marred by dust and sweat and blood... Theodore RooseveltThe Scary DBAAuthor of: SQL Server 2017 Query Performance Tuning, 5th Edition and SQL Server Execution Plans, 3rd EditionProduct Evangelist for Red Gate Software

Sporidium SSCommitted Points: 1550 More actions · Answer 2

Thanks Grant - you're right, a REBUILD will write far more pages than a REORGANIZE, probably all of them in the table/index concerned. I was just hoping that those few pages moved by a reorg might have had their checksums set, to incrementally increase the amount of corruption detection slowly over time. It wouldn't cost a lot to do so.

Johan Bijnens SSC Guru Points: 134873 More actions · Answer 3

also to be kept in mind: heaps.

You should rebuild heaps too, to activate the checksum mechanism.

Alter table [yourschema].[yourtable] rebuild

Johan

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