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30-542: [REDACTED] Look up dbc in Wiktionary, the free dictionary. DBC may refer to: D ata b ase c onnection libraries, e.g., JDBC CAN DBC files, standardized ASCII files defining the format and purpose of CAN bus messages IATA code for Baicheng Chang'an Airport dBc , decibels relative to carrier, a measurement in RF engineering dB(C) , C-weighted decibels,

60-415: A connection string , which is a way of addressing a specific database or server and instance as well as user authentication credentials (for example, Server= sql_box; Database= Common; User ID= uid; Pwd= password; ). Once a connection has been built it can be opened and closed at will, and properties (such as the command time-out length, or transaction , if one exists) can be set. The Connection String

90-446: A connection for too long when too many clients attempt to access the web site or one or more operations are blocked or simply inefficient. Database transaction A database transaction symbolizes a unit of work , performed within a database management system (or similar system) against a database , that is treated in a coherent and reliable way independent of other transactions. A transaction generally represents any change in

120-474: A database. Transactions in a database environment have two main purposes: In a database management system, a transaction is a single unit of logic or work, sometimes made up of multiple operations. Any logical calculation done in a consistent mode in a database is known as a transaction. One example is a transfer from one bank account to another: the complete transaction requires subtracting the amount to be transferred from one account and adding that same amount to

150-517: A human protein DBCS (disambiguation) Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title DBC . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=DBC&oldid=1192767500 " Category : Disambiguation pages Hidden categories: Short description

180-464: A layered system architecture (e.g., with one operation at the database-engine level, one operation at the operating-system level). Another type of transaction is the compensating transaction . Transactions are available in most SQL database implementations, though with varying levels of robustness. For example, MySQL began supporting transactions from early version 3.23, but the InnoDB storage engine

210-472: A loudness measurement in acoustics DBC News , a Bangladeshi news channel DBC Pierre (born 1961), Australian-born author Dead Brain Cells , a Canadian thrash metal band Design by contract , a methodology for designing computer software Detroit Boat Club , a historic rowing club Digital Broadcasting Corporation (Hong Kong) , a radio broadcasting corporation Dread Broadcasting Corporation ,

240-407: A transaction ID or XID. There are multiple varying ways for transactions to be implemented other than the simple way documented above. Nested transactions , for example, are transactions which contain statements within them that start new transactions (i.e. sub-transactions). Multi-level transactions are a variant of nested transactions where the sub-transactions take place at different levels of

270-438: A transaction might consist of one or more data-manipulation statements and queries, each reading and/or writing information in the database. Users of database systems consider consistency and integrity of data as highly important. A simple transaction is usually issued to the database system in a language like SQL wrapped in a transaction, using a pattern similar to the following: A transaction commit operation persists all

300-406: Is serializability , which guarantees that the effect of concurrent transactions is equivalent to their serial (i.e. sequential) execution. Most modern relational database management systems support transactions. NoSQL databases prioritize scalability along with supporting transactions in order to guarantee data consistency in the event of concurrent updates and accesses. In a database system,

330-425: Is composed of a set of key/value pairs as dictated by the data access interface and data provider being used. Many databases (such as PostgreSQL ) only allow one operation to be performed at a time on each connection. If a request for data (a SQL Select statement) is sent to the database and a result set is returned, the connection is open but not available for other operations until the client finishes consuming

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360-480: Is crucial, as it offers a virtually infinite pool of storage resources, accommodating a range of cloud-based data store classes with varying availability, scalability, and ACID properties. This integration is essential for achieving higher availability, lower response time, and cost efficiency in data-intensive applications deployed across cloud-based data stores. The Namesys Reiser4 filesystem for Linux supports transactions, and as of Microsoft Windows Vista ,

390-488: Is different from Wikidata All article disambiguation pages All disambiguation pages Database connection Connections are a key concept in data-centric programming. Since some DBMS engines require considerable time to connect, connection pooling was invented to improve performance. No command can be performed against a database without an "open and available" connection to it. Connections are built by supplying an underlying driver or provider with

420-477: Is inefficient for an application to create, use, and close a database connection whenever it needs to update a database. Connection pooling is a technique designed to alleviate this problem. A pool of database connections can be created and then shared among the applications that need to access the database. The connection object obtained from the connection pool is often a wrapper around the actual database connection. The wrapper understands its relationship with

450-464: The ACID properties over multiple nodes, and might include systems such as databases, storage managers, file systems, messaging systems, and other data managers. In a distributed transaction there is typically an entity coordinating all the process to ensure that all parts of the transaction are applied to all relevant systems. Moreover, the integration of Storage as a Service (StaaS) within these environments

480-705: The UKs first black music radio station The Devastating Beat Creator, stage name of Martin Nemley, a member of the American hip hop band Stetsasonic Direct Bonded Copper, a power electronic substrate Direct-buried cable , a kind of electrical cable See also [ edit ] DBC 1012 , a computer produced by Teradata Corporation in the early 1980s DBC1 , a human protein Deleted in Breast Cancer 1 ,

510-417: The acronym ACID . Databases and other data stores which treat the integrity of data as paramount often include the ability to handle transactions to maintain the integrity of data. A single transaction consists of one or more independent units of work, each reading and/or writing information to a database or other data store. When this happens it is often important to ensure that all such processing leaves

540-509: The database is always in a consistent state, even in the event of concurrent updates and failures. All the write operations within a transaction have an all-or-nothing effect, that is, either the transaction succeeds and all writes take effect, or otherwise, the database is brought to a state that does not include any of the writes of the transaction. Transactions also ensure that the effect of concurrent transactions satisfies certain guarantees, known as isolation level . The highest isolation level

570-493: The database or data store in a consistent state. Examples from double-entry accounting systems often illustrate the concept of transactions. In double-entry accounting every debit requires the recording of an associated credit. If one writes a check for $ 100 to buy groceries, a transactional double-entry accounting system must record the following two entries to cover the single transaction: A transactional system would make both entries pass or both entries would fail. By treating

600-416: The lowest level ( READ UNCOMMITTED ), which may occasionally be used to ensure high concurrency, such changes will be immediately visible. Relational databases are traditionally composed of tables with fixed-size fields and records. Object databases comprise variable-sized blobs , possibly serializable or incorporating a mime-type . The fundamental similarities between Relational and Object databases are

630-427: The methods on the wrapper object. This approach encourages the practice of opening a connection in an application only when needed, and closing it as soon as the work is done, rather than holding a connection open for the entire life of the application. In this manner, a relatively small number of connections can service a large number of requests. This is also called multiplexing . In a client/server architecture, on

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660-421: The other hand, a persistent connection is typically used so that server state can be managed. This "state" includes server-side cursors, temporary products, connection-specific functional settings, and so on. An application failure occurs when the connection pool overflows. This can occur if all of the connections in the pool are in use when an application requests a connection. For example, the application may use

690-412: The other. A database transaction, by definition, must be atomic (it must either be complete in its entirety or have no effect whatsoever), consistent (it must conform to existing constraints in the database), isolated (it must not affect other transactions) and durable (it must get written to persistent storage). Database practitioners often refer to these properties of database transactions using

720-435: The pool, and hides the details of the pool from the application. For example, the wrapper object can implement a "close" method that can be called just like the "close" method on the database connection. Unlike the method on the database connection, the method on the wrapper may not actually close the database connection, but instead return it to the pool. The application need not be aware of the connection pooling when it calls

750-471: The recording of multiple entries as an atomic transactional unit of work the system maintains the integrity of the data recorded. In other words, nobody ends up with a situation in which a debit is recorded but no associated credit is recorded, or vice versa. A transactional database is a DBMS that provides the ACID properties for a bracketed set of database operations (begin-commit). Transactions ensure that

780-414: The result set. Other databases, like SQL Server 2005 (and later), do not impose this limitation. However, databases that provide multiple operations per connection usually incur far more overhead than those that permit only a single operation task at a time. Database connections are finite and expensive and can take a disproportionately long time to create relative to the operations performed on them. It

810-441: The results of data manipulations within the scope of the transaction to the database. A transaction rollback operation does not persist the partial results of data manipulations within the scope of the transaction to the database. In no case can a partial transaction be committed to the database since that would leave the database in an inconsistent state. Internally, multi-user databases store and process transactions, often by using

840-481: The start and the commit or rollback . After starting a transaction, database records or objects are locked, either read-only or read-write. Reads and writes can then occur. Once the transaction is fully defined, changes are committed or rolled back atomically , such that at the end of the transaction there is no inconsistency . Database systems implement distributed transactions as transactions accessing data over multiple nodes. A distributed transaction enforces

870-405: Was disabled with the start of a transaction, autocommit will also be re-enabled with the end of the transaction. One can set the isolation level for individual transactional operations as well as globally. At the highest level ( READ COMMITTED ), the result of any operation performed after a transaction has started will remain invisible to other database users until the transaction has ended. At

900-506: Was not default before version 5.5. The earlier available storage engine, MyISAM does not support transactions. A transaction is typically started using the command BEGIN (although the SQL standard specifies START TRANSACTION ). When the system processes a COMMIT statement, the transaction ends with successful completion. A ROLLBACK statement can also end the transaction, undoing any work performed since BEGIN . If autocommit

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