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Multiversion Concurrency Control
Multiversion concurrency control (MCC or MVCC), is a non-locking concurrency control method commonly used by database management systems to provide concurrent access to the database and in programming languages to implement transactional memory. Description Without concurrency control, if someone is reading from a database at the same time as someone else is writing to it, it is possible that the reader will see a half-written or inconsistent piece of data. For instance, when making a wire transfer between two bank accounts if a reader reads the balance at the bank when the money has been withdrawn from the original account and before it was deposited in the destination account, it would seem that money has disappeared from the bank. Isolation is the property that provides guarantees in the concurrent accesses to data. Isolation is implemented by means of a concurrency control protocol. The simplest way is to make all readers wait until the writer is done, which is known as a rea ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-lock Concurrency Control
In Computer Science, in the field of databases, non-lock concurrency control is a concurrency control method used in relational databases without using lock (computer science), locking. There are several non-lock concurrency control methods, which involve the use of timestamps on transaction to determine transaction priority: * Optimistic concurrency control ** Timestamp-based concurrency control ** Validation-based concurrency control ** Multiversion concurrency control *** Snapshot isolation See also * Concurrency pattern * InterBase * Lock-free and wait-free algorithms References Concurrency control Transaction processing {{Database-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rust (programming Language)
Rust is a General-purpose programming language, general-purpose programming language emphasizing Computer performance, performance, type safety, and Concurrency (computer science), concurrency. It enforces memory safety, meaning that all Reference (computer science), references point to valid memory. It does so without a conventional Garbage collection (computer science), garbage collector; instead, memory safety errors and data races are prevented by the "borrow checker", which tracks the object lifetime of references Compiler, at compile time. Rust does not enforce a programming paradigm, but was influenced by ideas from functional programming, including Immutable object, immutability, higher-order functions, algebraic data types, and pattern matching. It also supports object-oriented programming via structs, Enumerated type, enums, traits, and methods. It is popular for systems programming. Software developer Graydon Hoare created Rust as a personal project while working at ... [...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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Version Control
Version control (also known as revision control, source control, and source code management) is the software engineering practice of controlling, organizing, and tracking different versions in history of computer files; primarily source code text files, but generally any type of file. Version control is a component of software configuration management. A ''version control system'' is a software tool that automates version control. Alternatively, version control is embedded as a feature of some systems such as word processors, spreadsheets, collaborative groupware, web docs, and content management systems, e.g., Help:Page history, Wikipedia's page history. Version control includes viewing old versions and enables Reversion (software development), reverting a file to a previous version. Overview As teams develop software, it is common to Software deployment, deploy multiple versions of the same software, and for different developers to work on one or more different versions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vector Clock
A vector clock is a data structure used for determining the partial ordering of events in a distributed system and detecting causality violations. Just as in Lamport timestamps, inter-process messages contain the state of the sending process's logical clock. A vector clock of a system of ''N'' processes is an array/vector of ''N'' logical clocks, one clock per process; a local "largest possible values" copy of the global clock-array is kept in each process. Denote VC_i as the vector clock maintained by process i, the clock updates proceed as follows: * Initially all clocks are zero. * Each time a process experiences an internal event, it increments its own logical clock in the vector by one. For instance, upon an event at process i, it updates VC_ \leftarrow VC_ + 1. * Each time a process sends a message, it increments its own logical clock in the vector by one (as in the bullet above, but not twice for the same event) then it pairs the message with a copy of its own vector ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Timestamp-based Concurrency Control
In computer science, a timestamp-based concurrency control algorithm is a optimistic concurrency control method. It is used in some databases to safely handle transactions using timestamps. Operation Assumptions * Every timestamp value is unique and accurately represents an instant in time. * A higher-valued timestamp occurs later in time than a lower-valued timestamp. Generating a timestamp A number of different approaches can generate timestamps * Using the value of the system's clock at the start of a transaction as the timestamp. * Using a thread-safe shared counter that is incremented at the start of a transaction as the timestamp. * A combination of the above two methods. Formal definition Each transaction (T_i) is an ordered list of actions (A_). Before the transaction performs its first action (A_), it is marked with the current timestamp, or any other strictly totally ordered sequence: TS(T_i) = NOW(). Every transaction is also given an initially empty set of transacti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Read-copy-update
In computer science, read-copy-update (RCU) is a synchronization mechanism that avoids the use of lock primitives while multiple threads concurrently read and update elements that are linked through pointers and that belong to shared data structures (e.g., linked lists, trees, hash tables). Whenever a thread is inserting or deleting elements of data structures in shared memory, all readers are guaranteed to see and traverse either the older or the new structure, therefore avoiding inconsistencies (e.g., dereferencing null pointers). It is used when performance of reads is crucial and is an example of space–time tradeoff, enabling fast operations at the cost of more space. This makes all readers proceed as if there were no synchronization involved, hence they will be fast, but also making updates more difficult. Name and overview The name comes from the way that RCU is used to update a linked structure in place. A thread wishing to do this uses the following steps: * create a n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Databases Using MVCC
The following database management systems and other software use multiversion concurrency control. Databases * Altibase * Berkeley DB * Cloudant * Cloud Spanner * Clustrix * CockroachDB * Couchbase * CouchDB * CUBRID * IBM Db2 – since IBM DB2 9.7 LUW ("Cobra") under CS isolation level – in ''currently committed'' modeDB2 Version 9.7 LUW Information CenterCurrently committed semantics improve concurrency/ref> * Drizzle * Druid * etcd * Exasol * eXtremeDB * Firebird * FLAIM * FoundationDB * GE Smallworld Version Managed Data Store * H2 Database Engine – experimental since version 1.0.57 (2007-08-25) * HBase * HSQLDB – starting with version 2.0 * IBM Netezza * Ingres * InterBase – all versions * LMDB * MariaDB (MySQL fork) – when used with XtraDB, an InnoDB fork and that is included in MariaDB sources and binaries oPBXT* MarkLogic Server – a bit of this is described in * MemSQL * Microsoft SQL Server – when using READ_COMMITTED_SNAPSHOT, starting wit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
InterBase
InterBase is a relational database management system (RDBMS) currently developed and marketed by Embarcadero Technologies. It runs on the operating systems Microsoft Windows, macOS, Linux, Oracle Solaris, Solaris, Android (operating system), Android, and iOS. Technology InterBase is a SQL-92-compliant relational database and supports standard interfaces such as JDBC, ODBC, and ADO.NET. History Multiversion concurrency control before InterBase Multiversion concurrency control is described in some detail in sections 4.3 and 5.5 of the 1981 paper "Concurrency Control in Distributed Database Systems" by Phil Bernstein, Philip Bernstein and Nathan Goodman while employed by the Computer Corporation of America. Bernstein and Goodman's paper cites a 1978 dissertation by D.P. Reed, which describes Multiversion concurrency control, MVCC and claims it as an original work. Early years Jim Starkey was working at Digital Equipment Corporation, DEC on their DATATRIEVE 4th generation languag ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Jim Starkey
Jim Starkey (born January 6, 1949, in Illinois) is a database architect responsible for developing InterBase, the first relational database to support multi-versioning,Babcock, Charles"MySQL Database to Get Replication Monitoring, Multiversioning Concurrency Features."InformationWeek. Sept. 14, 2007. Accessed Dec. 7, 2012 the blob column type, type event alerts, arrays and triggers.Niccolai, James"Update: MySQL buys company, hires noted architect."Computer World. Feb. 27, 2006. Accessed Dec. 7, 2012 Starkey is the founder of several companies, including the web application development and database tool company Netfrastructure and NuoDB. Education and career Jim Starkey graduated from University of Wisconsin at Madison, Wisconsin, with a Bachelor of Arts in Mathematics. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Digital Equipment Corporation
Digital Equipment Corporation (DEC ), using the trademark Digital, was a major American company in the computer industry from the 1960s to the 1990s. The company was co-founded by Ken Olsen and Harlan Anderson in 1957. Olsen was president until he was forced to resign in 1992, after the company had gone into precipitous decline. The company produced many different product lines over its history. It is best known for the work in the minicomputer market starting in the early 1960s. The company produced a series of machines known as the Programmed Data Processor, PDP line, with the PDP-8 and PDP-11 being among the most successful minis in history. Their success was only surpassed by another DEC product, the late-1970s VAX "supermini" systems that were designed to replace the PDP-11. Although a number of competitors had successfully competed with Digital through the 1970s, the VAX cemented the company's place as a leading vendor in the computer space. As microcomputers improved in t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Rdb
Oracle Rdb is a relational database management system for the OpenVMS operating system. It was originally released by Digital Equipment Corporation (DEC) in 1984 as VAX Rdb/VMS. Product history Rdb was a component of the ''VAX Information Architecture'', and was designed to interoperate with other Digital database tools and application frameworks such as the Application Control Management System, Datatrieve and the Common Data Dictionary. It originally provided a proprietary query interface known as the Relational Data Operator (RDO), but later gained support for ANSI SQL. In 1994 DEC sold the Rdb division to Oracle Corporation where it was rebranded Oracle Rdb. As of 2020, Oracle is still actively developing Rdb, with over half of the codebase developed under Oracle's ownership. It remains a VMS-only product; version 7.0 runs on OpenVMS for VAX and Alpha, version 7.1 on Alpha only, and versions 7.2 to 7.4 on Alpha and IA-64 (Itanium). Rdb featured one of the first cost- ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
