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gus bjorklund
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> On Apr 30, 2019, at 1:04 PM, George Potemkin wrote: > > MTX latch can be locked during BI writes that is true but does not happen for every before-image log write. mtx latch is, as rich says, designed to coordinate storing before-image note in before-image log buffer, storing same before-image note in after-iamge buffer, and making the recorded change to a database block. those 3 operations must all occur in the same order (for a given database block, the transaction log notes and the block changes must happen in the same order). note that writing to database, before-image log or after-image log is not required for those 3 things. there are various optimizations that are possible to reduce concurrency and make these things happen faster but the required ordering /must/ be preserved for crash recovery, rollback, and replication to work.
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