More on Steal and Force
| STEAL (why enforcing Atomicity is hard)
| To steal frame F: Current page in F (say P) is written to disk; some Xact holds lock on P.
| What if the Xact with the lock on P aborts?
| Must remember the old value of P at steal time (to support UNDOing the write to page P).
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| NO FORCE (why enforcing Durability is hard)
| What if system crashes before a modified page is written to disk?
| Write as little as possible, in a convenient place, at commit time,to support REDOing modifications. | | |
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