Precedence Graph

picture info	Precedence Graph A precedence graph, also named conflict graph and serializability graph, is used in the context of concurrency control in databases. The precedence graph for a schedule S contains: * A node for each committed transaction in S * An arc from Ti to Tj if an action of Ti precedes and conflicts with one of Tj's actions. That is the actions belong to different transactions, at least one of the actions is a write operation, and the actions access the same object (read or write). Precedence graph examples Example 1 :S = \begin T1 & T2 \\ R(A) & R(A) \\ A=A5 & R(B) \\ W(A) & B=B+A \\ R(B) & W(B) \\ B=B10 & \\ W(B) & \\ \end Example 2 :D = R1(A) R2(B) W2(A) Com.2 W1(A) Com.1 W3(A) Com.3 A precedence graph of the schedule D, with 3 transactions. As there is a cycle (of length 2; with two edges) through the committed transactions T1 and T2, this schedule (history) is ''not'' Conflict serializable. Notice, that the commit of Transaction 2 does not ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Serializability In concurrency control of databases,Philip A. Bernstein, Vassos Hadzilacos, Nathan Goodman (1987)''Concurrency Control and Recovery in Database Systems''(free PDF download), Addison Wesley Publishing Company, Gerhard Weikum, Gottfried Vossen (2001)''Transactional Information Systems'' Elsevier, transaction processing (transaction management), and various transactional applications (e.g., transactional memoryMaurice Herlihy and J. Eliot B. Moss. ''Transactional memory: architectural support for lock-free data structures.'' Proceedings of the 20th annual international symposium on Computer architecture (ISCA '93). Volume 21, Issue 2, May 1993. and software transactional memory), both centralized and distributed, a transaction schedule is serializable if its outcome (e.g., the resulting database state) is equal to the outcome of its transactions executed serially, i.e. without overlapping in time. Transactions are normally executed concurrently (they overlap), since this is the mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Concurrency Control In information technology and computer science, especially in the fields of computer programming, operating systems, multiprocessors, and databases, concurrency control ensures that correct results for concurrent operations are generated, while getting those results as quickly as possible. Computer systems, both software and hardware, consist of modules, or components. Each component is designed to operate correctly, i.e., to obey or to meet certain consistency rules. When components that operate concurrently interact by messaging or by sharing accessed data (in memory or storage), a certain component's consistency may be violated by another component. The general area of concurrency control provides rules, methods, design methodologies, and theories to maintain the consistency of components operating concurrently while interacting, and thus the consistency and correctness of the whole system. Introducing concurrency control into a system means applying operation constraints wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Database In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance. A database management system (DBMS) is the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS software additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an appli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Schedule (computer Science) In the fields of databases and transaction processing (transaction management), a schedule (or history) of a system is an abstract model to describe execution of transactions running in the system. Often it is a ''list'' of operations (actions) ordered by time, performed by a set of transactions that are executed together in the system. If the order in time between certain operations is not determined by the system, then a ''partial order'' is used. Examples of such operations are requesting a read operation, reading, writing, aborting, committing, requesting a lock, locking, etc. Not all transaction operation types should be included in a schedule, and typically only selected operation types (e.g., data access operations) are included, as needed to reason about and describe certain phenomena. Schedules and schedule properties are fundamental concepts in database concurrency control theory. Formal description The following is an example of a schedule: ;D In this example, the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Serializability In concurrency control of databases,Philip A. Bernstein, Vassos Hadzilacos, Nathan Goodman (1987)''Concurrency Control and Recovery in Database Systems''(free PDF download), Addison Wesley Publishing Company, Gerhard Weikum, Gottfried Vossen (2001)''Transactional Information Systems'' Elsevier, transaction processing (transaction management), and various transactional applications (e.g., transactional memoryMaurice Herlihy and J. Eliot B. Moss. ''Transactional memory: architectural support for lock-free data structures.'' Proceedings of the 20th annual international symposium on Computer architecture (ISCA '93). Volume 21, Issue 2, May 1993. and software transactional memory), both centralized and distributed, a transaction schedule is serializable if its outcome (e.g., the resulting database state) is equal to the outcome of its transactions executed serially, i.e. without overlapping in time. Transactions are normally executed concurrently (they overlap), since this is the mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Precedence Graph A precedence graph, also named conflict graph and serializability graph, is used in the context of concurrency control in databases. The precedence graph for a schedule S contains: * A node for each committed transaction in S * An arc from Ti to Tj if an action of Ti precedes and conflicts with one of Tj's actions. That is the actions belong to different transactions, at least one of the actions is a write operation, and the actions access the same object (read or write). Precedence graph examples Example 1 :S = \begin T1 & T2 \\ R(A) & R(A) \\ A=A5 & R(B) \\ W(A) & B=B+A \\ R(B) & W(B) \\ B=B10 & \\ W(B) & \\ \end Example 2 :D = R1(A) R2(B) W2(A) Com.2 W1(A) Com.1 W3(A) Com.3 A precedence graph of the schedule D, with 3 transactions. As there is a cycle (of length 2; with two edges) through the committed transactions T1 and T2, this schedule (history) is ''not'' Conflict serializable. Notice, that the commit of Transaction 2 does not ha ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Abraham Silberschatz Avi Silberschatz (born in Haifa, Israel) is an Israeli computer scientist and researcher. He graduated in 1976 with a Ph.D. in Computer Science from the State University of New York (SUNY) at Stony Brook. He became the Sidney J. Weinberg Professor of Computer Science at Yale University, USA in 2005. He was the chair of the Computer Science department at Yale from 2005 to 2011. Prior to coming to Yale in 2003, he was the Vice President of the Information Sciences Research Center at Bell Labs. He previously held an endowed professorship at the University of Texas at Austin, where he taught until 1993. His research interests include database systems, operating systems, storage systems, and network management. Silberschatz was elected an ACM Fellow ACM or A.C.M. may refer to: Aviation * AGM-129 ACM, 1990–2012 USAF cruise missile * Air chief marshal * Air combat manoeuvring or dogfighting * Air cycle machine * Arica Airport (Colombia) (IATA: ACM), in Arica, Amazonas, Colombia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
	Henry Korth Henry may refer to: People * Henry (given name) Henry (surname) Henry Lau, Canadian singer and musician who performs under the mononym Henry Royalty * Portuguese royalty King-Cardinal Henry, King of Portugal Henry, Count of Portugal, Henry of Burgundy, Count of Portugal (father of Portugal's first king) Prince Henry the Navigator, Infante of Portugal Infante Henrique, Duke of Coimbra (born 1949), the sixth in line to Portuguese throne * King of Germany *Henry the Fowler (876–936), first king of Germany King of Scots (in name, at least) Henry Stuart, Lord Darnley (1545/6–1567), consort of Mary, queen of Scots Henry Benedict Stuart, the 'Cardinal Duke of York', brother of Bonnie Prince Charlie, who was hailed by Jacobites as Henry IX * Four kings of Castile: Henry I of Castile Henry II of Castile Henry III of Castile Henry IV of Castile * Five kings of France, spelt ''Henri'' in Modern French since the Renaissance to italianize the name and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]
picture info	Database Management Systems In computing, a database is an organized collection of data stored and accessed electronically. Small databases can be stored on a file system, while large databases are hosted on computer clusters or cloud storage. The design of databases spans formal techniques and practical considerations, including data modeling, efficient data representation and storage, query languages, security and privacy of sensitive data, and distributed computing issues, including supporting concurrent access and fault tolerance. A database management system (DBMS) is the software that interacts with end users, applications, and the database itself to capture and analyze the data. The DBMS software additionally encompasses the core facilities provided to administer the database. The sum total of the database, the DBMS and the associated applications can be referred to as a database system. Often the term "database" is also used loosely to refer to any of the DBMS, the database system or an applicatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu]