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Topic: Concurrency control

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	Concurrency Control for Step-Decomposed Transactions - Bernstein, Gerstl, Lewis (ResearchIndex)
		In this paper we describe a new concurrency control that guarantees that only the allowable interleavings specified for an application occur The...
		23 Modular concurrency control and failure recovery (context) - Sha, Lehoczky et al.
		1 The performance of a concurrency control algorithm that expl..
	citeseer.ist.psu.edu /bernstein99concurrency.html (744 words)

	ASP.NET Optimistic Concurrency Control - The Code Project - ASP.NET
		Pessimistic concurrency control - a row is unavailable to users from the time the record is fetched until it is updated in the database.
		We have to keep in mind that an application that holds locks for long periods is not scalable, but this concurrency control schema might have to be implemented on some portions of the application.
		Concurrency control increases the application's complexity, debugging and maintenance, but your users will have a better experience using it.
	www.codeproject.com /aspnet/Concurrency_Control.asp (1827 words)

	Introduction to Concurrency Control
		Concurrency control deals with the issues involved with allowing multiple people simultaneous access to shared entities, be they objects, data records, or some other representation.
		To understand how to implement concurrency control within your system you must start by understanding the basics of collisions – you can either avoid them or detect and then resolve them.
		An important message of this article is that on modern software development projects that concurrency control and transactions are not simply the domain of databases, instead they are issues that are potentially pertinent to all of your architectural tiers.
	www.agiledata.org /essays/concurrencyControl.html (1786 words)

	Concurrency Control and Data Integrity
		The way in which the concurrent access to data is managed is governed by concurrency control.
		The main advantage of optimistic concurrency control method is faster response time, but on the downside you cannot be sure that the action will be performed until the lock has been accepted or rejected.
		For example, if there are many users, the probability of concurrent access is greater and so pessimistic concurrency control might be used, whereas if many users don't exist, concurrent access will be rarer so optimistic concurrency control might be better used.
	www.pramati.com /docstore/1230022/tref_concurrency.htm (1774 words)

	Concurrency Control for XML
		In particular, several papers discussed on this page have shown that classic concurrency control mechanisms developed for relational, hierarchical, and object oriented databases are no longer adequate for semi-structured databases.
		Kuen-Fang Jea, Shih-Ying Chen and Sheng-Hsien Wang, Concurrency Control in XML Document Databases: XPath Locking Protocol, In: Proceedings of the 9th International Conference on Parallel and Distributed Systems (ICPADS 2002), Taiwan, ROC, December 17-20, pp.
		Eun-Hye Choi and Tatsunori Kanai, XPath-based Concurrency Control for XML Data, In: Proceedings of the 14th Data Engineering Workshop (DEWS 2003), Kaga city, Ishikawa, Japan, March 3-5, 2003.
	www.sci.usq.edu.au /staff/dekeyser/concurrencyXML.html (675 words)

	O/R mappers and concurrency control - Frans Bouma's blog
		This means that, besides the point that there is no silver bullet to solve all concurrency problems, it is also not possible to define a common way to supply concurrency control: different developers will implement concurrency control differently, or at least: want to use it differently.
		Concurrency control as flexible as you can possibly get, and usable not only on a per-type basis but also on a per-instance basis.
		If you want higher level concurrency functionality, it is not wise to implement that on a low level, so it's in all cases more wise to simply add logic which prevents low level concurrency violations pop up like multi-edits of the same row.
	weblogs.asp.net /fbouma/archive/2004/03/06/85125.aspx (1849 words)

	Mimer Developers - Features - Transaction Concurrency - Optimistic Concurrency Control
		In a pessimistic concurrency control system, it is possible to get into a situation where a number of transactions are waiting on each other, a situation known as a deadlock, where none of the transactions can proceed.
		Through the use of optimistic concurrency control, Mimer SQL is able to avoid problems such as data being left inaccessible because of locks being held over user interactions or client processes failing.
		A solution to lock thrashing offered by the vendors to their customers, is to reduce the number of concurrent transactions in the system by restricting the number of server sessions, that is, throttle the throughput of the database server.
	developer.mimer.se /features/feature_15.htm (1596 words)

	Mimer Developers - Features - Transaction Concurrency - Optimistic Concurrency Control
		In a pessimistic concurrency control system, it is possible to get into a situation where a number of transactions are waiting on each other, a situation known as a deadlock, where none of the transactions can proceed.
		Through the use of optimistic concurrency control, Mimer SQL is able to avoid problems such as data being left inaccessible because of locks being held over user interactions or client processes failing.
		A solution to lock thrashing offered by the vendors to their customers, is to reduce the number of concurrent transactions in the system by restricting the number of server sessions, that is, throttle the throughput of the database server.
	developer.mimer.com /features/feature_15.htm (1596 words)

	Citations: Multiversion Concurrency Control -- Theory and Algorithms - Bernstein, Goodman (ResearchIndex)
		Bernstein and N. Goodman, "Multiversion Concurrency Control - Theory and Algorithms.," ACM Trans.
		Bernstein and N. Goodman, "Multiversion concurrency control---theory and algorithms," ACM Trans.
		In the existing concurrency control protocols based on multiversions such as MV2PL and MVTO, only the most recently committed versions of data items are used and the history such as H 2 cannot be generated.
	citeseer.ist.psu.edu /context/66385/0 (2983 words)

	Dr. Dobb's \| Object Concurrency Control 101 \| January 1, 2001
		Pessimistic concurrency control locks the source for the entire time that a copy of it exists, not allowing other copies to exist until the copy with the lock has finished its transaction.
		For object concurrency control to be successful, all of your developers must follow the same strategy.
		Your object concurrency control strategy should be implemented in a common application framework or reusable component that everyone uses in their code.
	www.ddj.com /dept/architect/184414697 (1812 words)

	Concurrency Control And Recovery in Database Systems \| FreeTechBooks.com
		Concurrency Control and Recovery In Database Systems by Philip A. Bernstein, Vassos Hadzilacos, and Nathan Goodman, is now available for free download, subject to the notice that appears on the book's copyright page.
		It does this by controlling the interleaving of concurrent transactions, to give the illusion that transactions execute serially, one after the next, with no interleaving at all.
		A recovery algorithm monitors and controls the execution of programs so that the database includes only the results of transactions that run to a normal completion.
	www.freetechbooks.com /about294.html (541 words)

	Computing Students - Notes - Transaction Management and Concurrency Control
		Concurrency Control is the process of managing / controlling simultaneous operations on the database.
		Concurrency control is required because actions from different users / applications taking place upon the database must not interfere.
		The two main concurrency control techniques are Locking and Timestamping
	www.computingstudents.com /notes/database_systems/transaction_management_concurrency_control.php (426 words)

	Not just another concurrency book (Site not responding. Last check: )
		Yet, when concurrency issues do arise, they are often of such urgency and intensity that they can overwhelm a project team, and, in some exceptional cases, sink an entire project.
		The most obvious change is to the concurrency environment and the level of control that the developer has over the elements of concurrency.
		Concurrency in JDK 5.0 (Brian Goetz, developerWorks, November 2004): Learn how the major enhancements to can help make your code faster, more scalable, more reliable, and easier to maintain.
	www.ibm.com /developerworks/java/library/j-goetzbook.html?ca=drs- (1394 words)

	DB2 for z/OS: DB2 Universal Database concurrency (Site not responding. Last check: )
		Concurrency is the ability of a database management system to allow multiple users to access data at the same time while maintaining the integrity and consistency of the data.
		Without an effective means of controlling concurrency, the integrity and consistency of the data could be compromised.
		Exclusive locks are associated with write operations, which means that the application holding the lock is eligible to update the data, and that the data is unavailable to other applications until the update is complete (the change is committed to the database) and the lock is released by the lock owner.
	www.ibm.com /developerworks/db2/library/techarticle/dm-0406whitlark/index.html (8787 words)

	Database Concurrency and Row Level Versioning in SQL Server 2005: Microsoft TechNet SQL Server TechCenter
		Concurrency is impacted when a process that is changing data prevents other processes from reading the data being changed or when a process that is reading data prevents other processes from changing that data.
		Concurrency is also impacted when multiples processes are attempting to change the same data concurrently and they cannot all succeed without sacrificing data consistency.
		Pessimistic concurrency control works on the assumption that there are enough data modification operations in the system to make it likely that any given read operation will be affected impacted by a data modification made by another user.
	www.microsoft.com /technet/prodtechnol/sql/2005/cncrrncy.mspx (7284 words)

	Working with Data and ASP.NET 2.0: ASP.NET Web: The Official Microsoft ASP.NET 2.0 Site (Site not responding. Last check: )
		Optimistic Concurrency — assume that while there may be concurrency conflicts every now and then, the vast majority of the time such conflicts won’t arise; therefore, if a conflict does arise, simply inform the user that their changes can’t be saved because another user has modified the same data
		Optimistic concurrency control works by ensuring that the record being updated or deleted has the same values as it did when the updating or deleting process started.
		With optimistic concurrency control, when a user deletes a product, the original product values — those that were present when the data was read from the database and assigned to the DataList — are compared against the current database values.
	www.asp.net /learn/dataaccess/tutorial41vb.aspx?tabid=63 (3740 words)

	Multiversion Concurrency Control Before InterBase
		I've been doing some reading in the area of concurrency theory, and, interestingly, have found some citations on the use of multiple record versions for concurrency control and recovery which predate InterBase.
		Multiversion concurrency control is described in some detail 4.3 and 5.5 of this 1981 paper by Philip Bernstein and Nathan Goodman -- then employed by the Computer Corporation of America.
		He had published a claiming there only two or three four ways to concurrency control, only so many ways to recovery, etc., so there were only a small number of ways to write a database system, so people were wasting their time thinking out it any.
	blogs.teamb.com /craigstuntz/archive/2005/02/18/MultiversionConcurrencyControlBeforeInterBase.aspx (1113 words)

	Concurrency Control
		The function of controlling these steps is given to the scheduler component of the DBMS, and the general process of assuring that transactions preserve consistency when executing simultaneou sly is called concurrency control.
		This project discusses two topics: (1) The topic of concurrency control in relational database management systems and how transaction journaling can be used to recover lost data or restore an inconsistent database to a consistent state.
		Concurrency control deals with preventing concurrently running processes from improperly inserting, deleting, or updating the same data.
	teradata.uark.edu /research/guo/control.html (2502 words)

	Modula-2 tutorial: Loops and Control Structures
		This is a rather large program compared to the ones we have seen so far, but I felt it would be better to cover all of the loops in one file than have you compile and run 4 different files.
		If program control comes here, it has a further expression to evaluate, which if TRUE, will cause the statements immediately following its THEN to be executed.
		It is simple to follow the flow of control, and the program itself needs no comments because of the judicious choice of variable names.
	www.modula2.org /tutor/chapter4.php (2646 words)

	Introduction to Data Concurrency in ADO.NET
		Pessimistic concurrency control: A row is unavailable to users from the time the record is fetched until it is updated in the database.
		Pessimistic concurrency is also useful for situations where it is detrimental for the record to change during the course of a transaction.
		However, pessimistic concurrency control is not possible in a disconnected architecture.
	msdn2.microsoft.com /en-us/library/cs6hb8k4(VS.80).aspx (1478 words)

	Concurrency Control in Real Time Databases (Site not responding. Last check: )
		The Speculative Concurrency Control approach relies on the use of redundant computations to start on alternative schedules, as soon as conflicts that threaten the consistency of the database are detected.
		A related topic is the index based concurrency control research on which is being conducted by the RICC group at the Indian Institute of Science and Indian Institute of Technology, Bombay, India.
		Studies on a predeclaration based concurrency control protocol is being conducted at the Bilknet University, Turkey and Technical UNIVERSITY Darmstadt, Germany.
	www.cs.uah.edu /~thinke/CS687/Fall97/Tech/abraham.html (2092 words)

	Concurrency - Haskell Prime - Trac (Site not responding. Last check: )
		concurrent foreign calls are required to guarantee timely responsiveness of an interactive application in the presence of long-running foreign calls.
		Portability problems: if a programmer develops a concurrent application on a preemptive system, there is no guarantee that it will work as expected on a cooperative system, and the compiler/runtime can give no useful feedback.
		Concurrent calls allow the progress guarantee to be retained in the presence of a blocking foreign call.
	hackage.haskell.org /trac/haskell-prime/wiki/Concurrency (1753 words)

	How Visual Studio .NET Generates SQL Statements for Concurrency Control
		For example, if you cleared the Use optimistic concurrency option when the adapter was originally configured, it will automatically be selected if you reconfigure it, even if you do not access the Advanced SQL Generation Options dialog box.
		When commands are generated to use optimistic concurrency, no verification will be performed on binary columns to determine whether concurrent changes have been made.
		If the "check all values" approach to optimistic concurrency proves inefficient, you can modify the generated command text so it does not have to check every original value against the values in the data source.
	msdn.microsoft.com /library/en-us/dv_vstechart/html/vbtchConcurrencyInADONET.asp?frame=true (1267 words)

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