Transaction Processing

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• A transaction is a collection of operations on the physical and abstract application state. ACID Atomicity. A transaction's changes to the state are atomic: either all happen or none happen. These changes include database changes, messages, and actions on transducers. Consistency. A transaction is a correct transformation of the state. The actions taken as a group do not violate any of the integrity constrains associated with the state. This requires that the transaction be a correct program. Isolation. Even though transactions execute concurrently, it appears to each transaction, T, that others executed either before T or after T, but not both. Durability. Once a transaction completes successfully(commits), its changes to the state survive failures. (查看原文)

  kainan 1赞 2014-01-21 08:32:49

• Christian wedding ceremony is a two-phase commit protocol: it has a voting phase, in which all participants prepare to commit, followed by a second commit phase, in which they execute the commit. A distinguished process acts much as the minister, coordinating the commit. The transaction concept is the computer equivalent to contract law. If nothing ever goes wrong, contracts are just overhead. But if something doesn't quite work,the contract specifies how to clean up the situation. (查看原文)

  kainan 1赞 2014-01-21 08:32:49