A.H. Skarra and S.B. Zdonik. Concurrency Control and Object-Oriented Databases. In Kim and Lochovsky [KL89], pp. 395--421.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....serializability classes. We conclude with a summary of our results. 2. BACKGROUND AND MOTIVATION Semantics based concurrency control protocols can be broadly classified into two groups depending on whether they are based upon the semantics of transactions or upon the semantics of objects [33]. Using semantics of transactions to increase concurrency in database systems was first proposed by Lainport [25] He discussed the example of an audit transaction and showed how its semantics could be used to execute it concurrently with certain transfer transactions. Gray [12] demonstrated the ....

SKARRA, A. H., AND ZDONn<, S. B Concurrency control and object-oriented databases. In Object-Oriented Concepts. Databases, and Applications, W. Kim and F. H Lochovsky, Eds., ACM Press, New York, 1989, 395 421.

....concurrency control mechanisms with a range of lock modes of varying exclusiveness. The transaction groups model proposed for the ObServer system replaces classical locks with lock mode, communication mode pairs to support the implementation of a nested framework for cooperating transactions [Skarra and Zdonik 89; Fernandez and Zdonik 89] A transaction group (TG) is defined as a process that controls the access of a set of cooperating transactions (members of the transaction group) to objects from the object server. Since a TG can include other TGs, a tree of TGs is composed. Within each TG, member ....

Skarra, A. H., and Zdonik, S. B. Concurrency Control and ObjectOriented Databases. In Kim, W., and Lochovsky, F. H., Ed., Object-Oriented Concepts, Databases, and Applications, ACM Press, New York, NY, 1989, pp. 395-421.

....transaction and the CP which defines the synchronisation of the transaction with others (see below) the user who initiated the transaction as well as the user s role are associated with the transaction. This information is provided to users involved in a concurrency conflict (as an extension of [SZ89]) 11) Transactions are synchronized either in a pessimistic or optimistic way. In the pessimistic case attribute Locks describes the locks held by a transaction. In the optimistic case attribute Timestamps describes a set of timestamps. The last attribute parent contains the parent transaction ....

Skarra A. H., Zdonik S. B., Concurrency Control and Object Oriented Databases, in: W. Kim, F.H. Lochovsky (Eds.), Object Oriented Concepts, Databases and Applications, ACM Press, New York, 1989, pages 395-421.

....to support the requirements of cooperative work. The gist of many cooperative transactions models is that transactions are assigned to 2 groups, where the transactions within a group employ a different concurrency control policy among themselves than with respect to transactions in other groups [4, 14]. Concurrency control is typically relaxed within a group, e.g. allowing simultaneous updates to multiple versions of an object or allowing reads of uncommitted updates. Among groups, however, a stricter policy such as serializability is common. Cooperative transaction groups allow collaboration ....

Andrea H. Skarra and Stanley B. Zdonik. Concurrency Control and Object-Oriented Databases. Object-Oriented Concepts, Databases, and Applications. ACM Press, New York, 1989, pages 395-421, Chapter 16.

....a large number of entities and performing lengthy computations. In the next section, we review several approaches for dealing with this problem. 1. 6 Approaches to Deal With Long Transactions Detailed surveys of concurrency control methods that go beyond two phase locking can be found elsewhere (Skarra and Zdonik 1989; Berghouti and Kaiser 1991) In this section, we consider methods that provide more concurrency than two phase locking, and thus, help in coping with the problem of long transactions. 1.6.1 Relaxing the Consistency Requirements One class of solutions works by relaxing the serializability ....

Skarra, A. H. and Zdonik, S. B. 1989. Concurrency Control and Object-Oriented Databases. In Kim, W. and Lochovsky, F., editors, Object Oriented Concepts, Databases, and Applications, pages 395--421. ACM Press, New York.

.... type by providing him information about currently active working contexts, running transactions related to a user s working context, transactions requested by other developers (e.g. requested locks) and changed states of related documents (as an extension of the communication modes proposed in [SZ89]) For instance, a user performing an optimistic transaction then might decide to abort the optimistic transaction and to restart it with pessimistic control or even to contact other developers to discuss the planned modifications and to prepare the necessary merge activity. The synchronisation ....

A.H. Skarra, S.B. Zdonik, "Concurrency Control and Object Oriented Databases ", in: W. Kim, F.H. Lochovsky (ed.) Object Oriented Concepts, Databases and Applications, pp. 395-421, ACM Press, New York, 1989.

....used for applications that involve reactive (endless) open ended (longlived) and collaborative (interactive) activities. Hence, various extensions to the traditional model have been proposed, referred to herein as extended transactions [Mos81, VRS86, BKK85, PKH88, KLS90, GGK 91, BHMC90, FZ89, SZ89, Elm91] Compared to the traditional transaction model, these models associate broader interpretations with the four transaction notions mentioned above to provide enhanced functionality while increasing the potential for improved performance. Upon examining these ad hoc extensions to the ....

Skarra, A. and Zdonik, S. Concurrency Control and ObjectOriented Databases. In Object-Oriented Concepts, Databases, and Applications, pages 395--421. ACM Press, 1989.

.... approach to overcome concurrency limitations of traditional transaction models [SS84, Wei88, F O89, WS92, MRW 93, WC95] These techniques exploit either the semantics of methods defined on objects (data oriented approach) or the semantics of transactions (transaction oriented approach) SZ89] to enhance concurrency in object oriented database management systems (OODBMS) In the CoAct model [RKT 95, WK96] we have proposed to utilize semantics based transaction management concepts to relax the isolation property of traditional transaction models. CoAct provides a flexible ....

A. H. Skarra and S. B. Zdonik. Concurrency control and object-oriented databases. In Kim and Lochovsky [KL89], chapter 16, pages 395--421.

....O89, WS92, MRW 93, WC95] seem to be a promising approach to overcome concurrency limitations of traditional transaction models. These techniques exploit either the semantics of methods defined on objects (data oriented approach) or the semantics of transactions (transaction oriented approach) SZ89] to enhance concurrency in object oriented database management systems (OODBMS) In the COACT model [RKT 95, WK96] we have proposed to utilize semantics based transaction management concepts to relax the isolation property of traditional transaction models. COACT provides a flexible ....

A. H. Skarra and S. B. Zdonik. Concurrency control and object-oriented databases. In Kim and Lochovsky

....result from procedure calls. Recoverable Communicating Actions [18] which support arbitrary computation topologies, have been proposed in the context of distributed operating systems where interactions are more complex. Cooperative Transactions [3] Split Transactions [14] and Transaction Groups [6, 17] have also been suggested for capturing the interactions found in the new applications. Irrespective of how successful these extended transaction models are in supporting the systems that they were intended for, they merely represent points within the spectrum of interactions possible within ....

....Schemes In this section, the semantics of four transaction models are specified using the ACTA framework. These are Nested Transactions, Split Transactions, Recoverable Communicating Actions and Cooperative Transactions. Because of space limitations, the characterization of Transaction Groups [6, 17] and Multi Coloured Actions [16] are not included in this paper. Also, the properties of a new transaction model resulting from the combination of Nested Transactions and Split Transactions are studied in order to demonstrate the usefulness of our framework in reasoning about the properties of ....

Skarra, A. and Zdonik, S. Concurrency Control and Object-Oriented Databases. In Object-Oriented Concepts, Databases, and Applications, pages 395--421. ACM Press, 1989.

....Models of the data approach define concurrency properties on abstract data types according to the semantics of the type and its operations. Models of the transaction approach define concurrency properties on transactions according to the semantics of transactions and the data they manipulate. In [134] a transaction model for design applications in computer supported, cooperative environments is proposed for flexible concurrency control. The model exploits the special characteristics of design activities and design data, and maintains database consistency by adherence to semantic correctness ....

Skarra, A. H., and Zdonik, S. B. Concurrency Control and ObjectOriented Databases. In Kim and Lochovsky [90].

....modules induce static semantic errors in their own modules as soon as the individual editing commands have been entered [Kaiser 87] Another requirement of synergistic cooperation is to divide programmers, or at least the transactions they control, into groups. The transaction groups paradigm [Skarra 89] is one example of such a scheme, where serializability may be relaxed among transactions in the same group to allow concerted effort, but the transactions of different groups are isolated in the classical sense. Transaction groups can be implemented using the locking and communication ....

Andrea H. Skarra and Stanley B. Zdonik. Concurrency Control and Object-Oriented Databases. Object-Oriented Concepts, Databases, and Applications. ACM Press, New York, 1989, pages 395-421.

....as the correctness requirement. The characteristics of different applications call for different styles of cooperation. An application may call for several styles of cooperation among its activities simultaneously. Various extensions to the traditional transaction model have been proposed [16, 3, 18, 24, 10, 20, 8, 23, 22]. These, referred to herein as complex transactions, can provide the basis for realizing different styles of cooperation. Irrespective of how successful these extended transactions models are in supporting the systems that they were intended for, they were designed with particular situations in ....

Skarra A. and S. Zdonik. Concurrency Control and Object-Oriented Databases. In Object-Oriented Concepts, Databases, and Applications, pages 395--421. ACM Press, 1989.

....occur in performance critical OODBS applications, because transactions tend to be longer in applications with complex operations on complex objects. To avoid or alleviate potential data contention, the following issues must be addressed by an acceptable concurrency control protocol in OODBSs (cf. [SZ89]) 1. Object structure: Concurrency control should generally operate on objects rather than pages or storage atoms, thus making the additional data modeling power of OODBSs available to the transaction management. This objective entails the ability to exploit the structure of complex objects; ....

Skarra, A.H., Zdonik, S.B., Concurrency Control and Object-Oriented Databases, in: W. Kim, F.H. Lochovsky (eds.), Object-Oriented Concepts, Databases, and Applications, ACM Press, 1989

....exist in this area that also provide good support for long, interactive, and cooperative design processes. Of the two cooperation primitives, notification and groups, most of these approaches seem to focus a lot more on groups than on notification. Especially the transaction groups approach [SZ89, HZ87] and the tool kit concept [US92] put considerable effort into structuring transactions in trees. A problem that arises with this type of structure is that it does not model the real world correctly. The interactions among designers in a large software project, for example, cannot be ....

A.H. Skarra and S.B. Zdonik. Concurrency Control and Object-Oriented Databases. In W. Kim and F.H. Lochovsky, editors, Object-Oriented Concepts, Databases, and Applications, pages 395--421. ACM Press, New York, 1989.

....primarily motivated to use object based concurrency control to avoid the over 50 head of client server communication. Without a database server to manage concurrency, the database objects must supply their own concurrency control. In other words, the database objects should be atomic data types [92, 73]. An atomic data type is essentially a class whose methods guarantee serial behavior in the presence of concurrent requests. Since the concurrency control can be individually tailored according to the semantics of the class member functions, it is possible to achieve higher levels of concurrency ....

A. H. Skarra and S. B. Zdonik, "Concurrency control and object-oriented databases," in Object-Oriented Concepts, Databases, and Applications, W. Kim and F. H. Lochovsky, editors, pp. 395--421. Addison Wesley, 1989.

.... to extend the notion of nested supertransactions to allow interaction between Bob and Alice by treating their work on F, G, and the other modules as all transactions of the same supertransaction, and in fact such transaction grouping is the basis of many approaches to open ended activities [39, 14]. But both nested transactions and transaction groups presume that the structure of the set of (sub)transactions is known in advance, when the code is written. In contrast, we require support for unpredictable developments, where the durations and particularly the possible interactions are ....

Andrea H. Skarra and Stanley B. Zdonik. Concurrency Control and Object-Oriented Databases, pages 395--421. ACM Press, New York, 1989.

....durations, and cooperative in nature. Hence, interactions and visibility across such transactions have to be promoted rather than curtailed, and serializability as the correctness criterion needs to be relaxed. Thus, there was a recognition that the transaction concept itself had to be reexamined [3,16], as it combined several important notions such as visibility, permanence, recovery, and consistency. 2 The need for more flexible transaction models has resulted in various extensions and proposals to the traditional transaction model over the last decade [1,12] As is perhaps inevitable, these ....

A. H. Skarra and S. B. Zdonik, "Concurrency Control and Object-oriented databases," In Object-Oriented Concepts, Databases, and Applications, pages 395-421, ACM Press, 1989.

....of a process transaction and the CP used for the synchronisation of the transaction (see below) the user who initiated the transaction as well as the user s role are associated with the transaction. This information is provided to users involved in a concurrency conflict (as an extension of [11]) Transactions are synchronized either in a pessimistic or optimistic way. In the pessimistic case attribute Locks describes the locks held by a transaction. In the optimistic case attribute Timestamps describes a set of timestamps. The last attribute parent contains the parent transaction ....

.... the PSDE should support the user in choosing the most suitable type by providing him with information about currently active working contexts, transactions (and locks) requested by other developers, and state changes of related documents (as an extension of the communication modes proposed in [11]) For instance, a user performing an aCP transaction (optimistic mode) and getting this information might then decide to abort this transaction and to restart it with pessimistic control, or to contact other developers to discuss the planned modifications and to prepare the necessary merge ....

Skarra A. H., Zdonik S. B., Concurrency Control and Object Oriented Databases, in: W. Kim, F.H. Lochovsky (Eds.), Object Oriented Concepts, Databases and Applications, ACM Press, New York, 1989, pages 395-421.

....to reach moreoptimal# decisions. The clearest evidence of this trend is in the area of transaction management. A number of researchers are working on semantic transactions which exploit information onthe# behaviour of objects to increase the level of concurrency and the flexibility of transactions [50]. Early steps in this work was carried out in the Argus project [51] Argus allows types to be created out of in built atomic types. Atomic types provide fairly traditional mechanisms for maintaining consistency of the data. This is then enhanced by allowing users to define their own data types ....

Skarra, A.H., and S.B. Zdonik, "Concurrency Control and Object-Oriented Databases", Object-Oriented Concepts, Databases and Applications. Editor: W. Kim and F.H. Lochovsky. New York: ACM Press, Pages: 395-422.

....applications, a number of problems exist. For example, it is not clear in joint authoring applications whether locks should be applied at the granularity of sections, paragraphs, sentences or even words. A number of more radical schemes have also been proposed. For example, Skarra and Zdonik [47] have introduced the concept ofa# transaction group which co ordinates access to shared data for a number of co operating members. Within a transaction group, the notion of serialisability is replaced by access rules based on the semantics of the cooperation. Access rules provide the policy of ....

Skarra, A. and Zdonik, S. (1989) 'Concurrency Control and Object-Oriented Databases', in Kim, W. and Lochovsky, F.H. (eds), Object-Oriented Concepts, Databases, and Applications, ACM Press Frontier Series. Addison-Wesley, Pages: 395-421.

No context found.

A.H. Skarra and S.B. Zdonik. Concurrency Control and Object-Oriented Databases. In Kim and Lochovsky [KL89], pp. 395--421.

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SKZD89 Skarra A. H. and Zdonik S. B., Concurrency Control and Object-Oriented Databases, Object-Oriented Concepts, Databases and Applications, ACM Press, 1989.

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A. H. Skarra and S. B. Zdonik, #Concurrency Control and Object-oriented databases," In Object-Oriented Concepts, Databases, and Applications, pages 395-421, ACM Press, 1989.

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A. H. Skarra and S. B. Zdonik. Concurrency control and object-oriented databases. In Objectoriented concepts, Databases and Applications, pages 395--421, 1989.

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