Several protocols that ensure that a database can be recovered to a consistent state after a transaction failure or system crash are compared. The study includes a collection of simple analytic models, based on Markov...
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ISBN:
(纸本)0818605642
Several protocols that ensure that a database can be recovered to a consistent state after a transaction failure or system crash are compared. The study includes a collection of simple analytic models, based on Markov processes, for these protocols and some surprising results on the relative performance of the protocols. The authors consider only two-stage transactions (all reads before writes) and ignore effects of serializing transactions. The most interesting performance result presented is that, for systems.obeying the assumptions of this paper, the 'pessimistic' policy of holding write locks to commit point is considerably less efficient than the 'optimistic' policy that allows reading of uncommitted data but risks cascading aborts. A multiversion policy was also studied and found always to be nearly as good as the optimistic policy and sometimes much better.
作者：
McKendry, Martin S.Georgia Inst of Technology
Sch of Information & Computer Science Atlanta GA USA Georgia Inst of Technology Sch of Information & Computer Science Atlanta GA USA
Examples to illustrate requirements for ordering mechanisms are introduced. A model of nested actions is then used as a basis for categorizing visibility requirements. These requirements go beyond those typical of dat...
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ISBN:
(纸本)0818605642
Examples to illustrate requirements for ordering mechanisms are introduced. A model of nested actions is then used as a basis for categorizing visibility requirements. These requirements go beyond those typical of databasesystems. because often the entities managed by operating systems.cannot be recovered if an action fails. Several simplifications that apply to many operating system problems are discussed. Algorithms for controlling ordering are then presented, with examples of their use. Several expediencies that result from ordering requirements are established. In many situations, recovery for nested actions can be implemented with a single backup copy of each item, a single synchronization variable can be used to control blocking, and generalized locking is not required. These savings appear to be fundamental to making the object-action approach viable for operating system construction.
For performance evaluation of distributedsystems.and concurrency control mechanisms, several concurrent tree algorithms with dynamic, distributed concurrency control have been proposed that combine selective locking ...
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ISBN:
(纸本)0818605642
For performance evaluation of distributedsystems.and concurrency control mechanisms, several concurrent tree algorithms with dynamic, distributed concurrency control have been proposed that combine selective locking policies and 'built-in' recovery mechanisms in place of more centralized concurrency control. Claims have been made that such algorithms allow a high degree of reliability and an improved degree of concurrency over traditional approaches. Because concurrency control mechanisms regulate the potential interference between concurrent processes, they have a dramatic effect on these aspects of system performance. An evaluation methodology that has been used to test these claims is described. The methodology combines evaluation of a prototype implementation of a concurrent system with simulation of the system on a more ambitious scale using a general-purpose multiprocessor simulation system. Results for the particular system on the degree of concurrency, degree of interference, and frequency of recovery generally supports the performance claims for the distributed concurrency-control mechanisms.
作者：
Seifert, Manfred H.IBM Germany
Heidelberg Scientific Cent Heidelberg West Ger IBM Germany Heidelberg Scientific Cent Heidelberg West Ger
A characteristic feature of the dynamic structure of the distributedsoftware is, that management functions as well as application functions are carried out by parallel and interacting processes. A set of such interac...
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A characteristic feature of the dynamic structure of the distributedsoftware is, that management functions as well as application functions are carried out by parallel and interacting processes. A set of such interacting and belonging together processes is called a distributed process system. The application and system programs are defined and the structural-redundant process is explained including functional redundancy. User and manager process systems.are also considered in the architecture of fault-tolerant software.
The TABS prototype is an experimental facility that provides operating-system level support for distributed transactions operating on shared abstract types. It is hoped that the facility will simplify the construction...
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ISBN:
(纸本)0818605642
The TABS prototype is an experimental facility that provides operating-system level support for distributed transactions operating on shared abstract types. It is hoped that the facility will simplify the construction of available, reliable, distributed applications. The authors describe the TABS system model, the structure of the prototype, and certain aspects of its operation. They conclude with an evaluation of the status of the TABS project.
The concept of atomic transactions has been used to provide reliable processing in both centralized and distributedsystems. An extension of traditional atomic transactions is presented: nested transactions. Nested tr...
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The concept of atomic transactions has been used to provide reliable processing in both centralized and distributedsystems. An extension of traditional atomic transactions is presented: nested transactions. Nested transactions are seen to permit safe concurrency within as well as among transactions, and to enable transactions to fail partially in a graceful and controlled manner. These properties of nested transactions suit them to a number of distributed applications. Examples of such applications are described.
A database management system was designed and implemented for the 5ESS switching system. The database is distributed and subject to stringent real time constraints and reliability requirements. A relational model is c...
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ISBN:
(纸本)0818605014
A database management system was designed and implemented for the 5ESS switching system. The database is distributed and subject to stringent real time constraints and reliability requirements. A relational model is chosen for this specialized database management system. This paper focuses on the reliability aspects of the design and how the balance between real-time constraints and reliability requirements is maintained. The concurrency control mechanism plays a significant role in achieving that balance by providing real-time access to call processing and also maintaining a consistent view of the data.
In this paper the authors briefly present the design of a distributed relational data base system. Then, they discuss experimental observations of the performance of that system executing both short and long commands....
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In this paper the authors briefly present the design of a distributed relational data base system. Then, they discuss experimental observations of the performance of that system executing both short and long commands. Conclusions are also drawn concerning metrics that distributed query processing heuristics should attempt to minimize. Lastly, they comment on architectures which appear viable for distributed data base applications.
A technique is presented for estimating the performance of programs written for execution on fail-stop processors. It is based on modeling the program as a discrete-time Markov chain and then using z-transforms to der...
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ISBN:
(纸本)0818605642
A technique is presented for estimating the performance of programs written for execution on fail-stop processors. It is based on modeling the program as a discrete-time Markov chain and then using z-transforms to derive a probability distribution for time to completion. The use of z-transforms seems to have several potential advantages over the use of transition matrices, which is also discussed. Among these are the ease with which the transform associated with a program can be calculated, the simplicity of obtaining the mean and variance from the transform, and the promise of obtaining a closed form for the probability distribution. Nevertheless, the utility of the z-transform technique remains to be confirmed by its systematic application to realistic fault-tolerant programs.
作者：
Leitner, GeraldColumbia Univ
Dep of Computer Science New York NY USA Columbia Univ Dep of Computer Science New York NY USA
Many distributed applications are structured as a set of client processes generating requests for service, and a set of server processes servicing these requests. The common form of interprocess communication (IPC) be...
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ISBN:
(纸本)0818605642
Many distributed applications are structured as a set of client processes generating requests for service, and a set of server processes servicing these requests. The common form of interprocess communication (IPC) between two single processes does not provide adequate support for robustness and throughput optimization. The author presents a stylized form of IPC between a group of client processes and a group of server processes. The choice of a particular server process to service a request is made dynamically at run-time. This dynamic task distribution provides the kernel support needed to make individual failures of server processes transparent and to optimize system performance through load leveling. The semantics of stylized IPC and the high-level protocol to implement it are described. Particular emphasis is placed on minimizing the performance overhead incurred by this mechanism.
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