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Jim Beam
Posting Yak Master
137 Posts |
 Posted - 2011-01-05 : 08:35:11
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| Hi all,Am I correct in thinking that changes like Updates/Inserts etc are first done in cache, then to the T/Log, then to disk? |
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GilaMonster
Master Smack Fu Yak Hacker
4507 Posts |
Posted - 2011-01-05 : 09:16:46
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| Mostly yes.When a change is made the data pages are changed in cache and the associated log record is written to the log buffer. When the transaction that the change was part of commits, the log buffer is written to disk, to the log file. (This can happen before the commit also). At a later point, when a checkpoint runs or when the lazy writer starts up the modified data page is written to the data file.The log records are always written before the data pages. That's a hard requirement of the way SQL does IO, called write-ahead logging.--Gail ShawSQL Server MVP |
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Jim Beam
Posting Yak Master
137 Posts |
Posted - 2011-01-05 : 09:26:34
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| Cheers Gail, succinctly put! |
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Sequence of change commital