| dbpprop:abstract
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- In databases, transaction processing, and other distributed applications, global serializability is a property of a global schedule of transactions. A global schedule is the unified schedule of all the individual database schedules in a multidatabase environment. Complying with global serializability means that the global schedule is serializable, has the serializability property. This makes global serializability a major goal for global concurrency control in multidatabase systems. With the prolifaration of the Internet, Cloud computing, and small, portable, powerful computing devices the need for effective global serializability techniques to ensure correctness in and among distributed transactional applications seems to increase. In a federated database system or any other more loosely defined multidatabase system, which are typically distributed in a communication network, transactions span multiple databases. Enforcing global serializability in such system, where different databases may use different types of concurrency control, is problematic. Even if every local schedule of a single database is serializable, the global schedule of a whole system is not necessarily serializable. The massive communication exchanges of conflict information needed between databases to reach conflict serializability would lead to unacceptable performance, primarily due to computer and communication latency. Achieving global serializability effectively over different types of concurrency control has been open for several years. Commitment ordering (or Commit ordering; CO), a serializability technique introduced in 1991, provides an effective general solution for global serializability across any collection of database systems and other transactional objects, with possibly different concurrency control mechanisms. CO does not need the distribution of conflict information, but rather utilizes the already needed (unmodified) atomic commitment protocol messages without any further communication between databases. It also allows optimistic (non-blocking) implementations. CO generalizes Strong strict two phase locking (SS2PL), which in conjunction with the Two-phase commit (2PC) protocol is the de facto standard for achieving global serializability across (SS2PL based) database systems. As a result CO compliant database systems (with any, different concurrency control types) can transparently join existing SS2PL based solutions for global serializability. The most significant aspects of CO that make it a uniquely effective general solution are: Seamless, low overhead integration with any concurrency control mechanism, with neither changing any transaction's operation scheduling or blocking it, nor adding any new operation. No need of conflict or equivalent information distribution. Automatic global deadlock resolution, and Scalability All these aspects, except the first, are also possessed by the popular SS2PL, which is a (constrained, blocking) special case of CO.
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![[RDF Data]](/statics/sw-cube.png)
