Database Management Systems · topic
ACID properties and transaction states, schedules and conflicts, precedence graphs, conflict and view serializability, counting schedules, and the recoverable, cascadeless and strict schedule classes with cascading rollback and isolation anomalies.
A transaction is a unit of program execution that reads and possibly updates database items and must behave as one indivisible step: either all of its effects persist or none do, and other transactions see it as if it ran alone.
Isolation says that concurrent transactions must behave as if they ran one at a time. Serializability makes this precise: a schedule is acceptable if it is equivalent to some serial schedule. Two notions of equivalence are used.
Serializability ignores failures: it assumes every transaction commits. A real system must also handle a transaction that aborts after other transactions have read what it wrote. Recoverability classifies schedules by how safely they survive such aborts, using the positions of commits and aborts.
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