Safe Commits

Keep Reads and Writes Behind the Boundary

Later reads and writes stay behind the prior writer's commit boundary in this toy value model.

highlighted = computed this step

Keep reads and writes behind the boundary

A stricter rule also keeps later writes behind the prior writer's commit boundary in this toy value model.

commit before later access\text{commit before later access}

Show the boundary

The schedule has 6 events. Each later access to the item waits behind the previous writer's commit.

events=6\text{events}=6

Safe commit and rollback schedules are tiny finite histories; logging, undo, ARIES, timing, isolation-level, product, and performance claims are out of scope.

Strict scheduleeventtxopitemvalue1T1wX102T1c3T2wX204T2c5T3rX6T3c reads-from factsreadEventreaderitemwriterwriteEventvalue5T3XT2320 external read dependencieswriterreaderitemwriteEventreadEventT2T3X35 classificationsfactvaluerecoverableyescascadelessyesstrictyes violationsnkindtx/readerwriteritemnonenonenonenonenone

Read the strict label

The strict classification is yes.

strict=yes\text{strict}=yes

Summary

No locks, timestamps, or logging mechanism is claimed; only the schedule property is classified.

property of the history\text{property of the history}