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Which mechanism does the DBMS most commonly use to honour the Durability property?
Aan in-memory hash table of recent writes
Ba separate process that polls and re-checks invariants
Ca write-ahead log that hits disk before the data file is finalised
Dcompile-time validation of every SQL statement
Answer & Solution
Correct answer: C. a write-ahead log that hits disk before the data file is finalised
Write-ahead logging (WAL) writes a log record describing the change before the actual data page is updated on disk. On crash recovery, the log is replayed to bring the database forward to its committed state. In-memory hash tables don't survive power cuts; invariant polling and compile-time checks address consistency, not durability.
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