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Redo Log
In the Oracle RDBMS environment, redo logs comprise files in a proprietary format which log a history of all changes made to the database. Each redo log file consists of redo records. A redo record, also called a redo entry, holds a group of change vectors, each of which describes or represents a change made to a single block in the database. For example, if a user UPDATEs a salary-value in a table containing employee-related data, the DBMS generates a redo record containing change-vectors that describe changes to the data segment block for the table. And if the user then COMMITs the update, Oracle generates another redo record and assigns the change a "system change number" (SCN). Whenever something changes in a datafile, Oracle records the change in the redo log. The name ''redo log'' indicates its purpose: If the database crashes, the RDBMS can redo (re-process) all changes on datafiles which will take the database data back to the state it was when the last redo record was ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Database
Oracle Database (commonly referred to as Oracle DBMS, Oracle Autonomous Database, or simply as Oracle) is a proprietary multi-model database management system produced and marketed by Oracle Corporation. It is a database commonly used for running online transaction processing (OLTP), data warehousing (DW) and mixed (OLTP & DW) database workloads. Oracle Database is available by several service providers on-premises, on-cloud, or as a hybrid cloud installation. It may be run on third party servers as well as on Oracle hardware ( Exadata on-premises, on Oracle Cloud or at Cloud at Customer). Oracle Database uses SQL for database updating and retrieval. History Larry Ellison and his two friends and former co-workers, Bob Miner and Ed Oates, started a consultancy called Software Development Laboratories (SDL) in 1977, later Oracle Corporation. SDL developed the original version of the Oracle software. The name ''Oracle'' comes from the code-name of a CIA-funded proj ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Change Data Capture
In databases, change data capture (CDC) is a set of software design patterns used to determine and track the data that has changed (the "deltas") so that action can be taken using the changed data. The result is a delta-driven dataset. CDC is an approach to data integration that is based on the identification, capture and delivery of the changes made to enterprise data sources. For instance it can be used for incremental update of data loading. CDC occurs often in data warehouse environments since capturing and preserving the state of data across time is one of the core functions of a data warehouse, but CDC can be utilized in any database or data repository system. Methodology System developers can set up CDC mechanisms in a number of ways and in any one or a combination of system layers from application logic down to physical storage. In a simplified CDC context, one computer system has data believed to have changed from a previous point in time, and a second computer syste ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transaction Log
In the field of databases in computer science, a transaction log (also transaction journal, database log, binary log or audit trail) is a history of actions executed by a database management system used to guarantee ACID properties over crashes or hardware failures. Physically, a log is a file listing changes to the database, stored in a stable storage format. If, after a start, the database is found in an inconsistent state or not been shut down properly, the database management system reviews the database logs for uncommitted transactions and rolls back the changes made by these transactions. Additionally, all transactions that are already committed but whose changes were not yet materialized in the database are re-applied. Both are done to ensure atomicity and durability of transactions. This term is not to be confused with other, human-readable logs that a database management system usually provides. In database management systems, a journal is the record of data al ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Database Tuning
Database tuning describes a group of activities used to optimize and homogenize the performance of a database. It usually overlaps with query tuning, but refers to design of the database files, selection of the database management system (DBMS) application, and configuration of the database's environment (operating system, CPU, etc.). Database tuning aims to maximize use of system resources to perform work as efficiently and rapidly as possible. Most systems are designed to manage their use of system resources, but there is still much room to improve their efficiency by customizing their settings and configuration for the database and the DBMS. I/O tuning Hardware and software configuration of disk subsystems are examined: RAID levels and configuration, block and stripe size allocation, and the configuration of disks, controller cards, storage cabinets, and external storage systems such as SANs. Transaction logs and temporary spaces are heavy consumers of I/O, and affect p ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Point-in-time Recovery
Point-in-time recovery (PITR) in the context of computers involves systems, often databases, whereby an administrator can restore or recover a set of data or a particular setting from a time in the past. Note for example Windows's capability to restore operating-system settings from a past date (for instance, before data corruption occurred). Time Machine for macOS provides another example of point-in-time recovery. Once PITR logging starts for a PITR-capable database, a database administrator can restore that database from backup In information technology, a backup, or data backup is a copy of computer data taken and stored elsewhere so that it may be used to restore the original after a data loss event. The verb form, referring to the process of doing so, is "wikt:back ...s to the state that it had at any time since. See also * Continuous data protection * Data version control References External links PostgreSQL Continuous Archiving and Point-in-Time Recovery (PI ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle LogMiner
Oracle LogMiner, a utility provided by Oracle Corporation to purchasers of its Oracle database, provides methods of querying logged changes made to an Oracle database, principally through SQL commands referencing data in Oracle redo logs. A GUI interface for the functionality comes with the Oracle Enterprise Manager product. LogMiner turns the concept and practices of data mining on the internal processes of the database itself. Database administrators can use LogMiner to: * identify the time of a database-event * isolate transactions carried out in error by users * determine steps needed for the recovery of inadvertent changes to data * assemble data on actual usage for use in performance-tuning and capacity-planning * audit An audit is an "independent examination of financial information of any entity, whether profit oriented or not, irrespective of its size or legal form when such an examination is conducted with a view to express an opinion thereon." Auditing al .. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Flashback
In Oracle databases, Flashback tools allow administrators and users to view and manipulate past states of an instance's data without (destructively) recovering to a fixed point in time. Compare the functionality of Oracle LogMiner, which identifies how and when data changed rather than its state at a given time. Flash Recovery Area Flashback requires the Flash Recovery Area (FRA), a storage area that allows Flash Backup and Recovery operations on Oracle databases. DBAs may configure the FRA on an ASM diskgroup or on local disk. It is a specific area of disk storage that is set aside exclusively for retention of backup components such as datafile image copies, archived redo logs, and control-file autobackup copies. The FRA feature is available from release Oracle 10g onwards. Availability Oracle Corporation Oracle Corporation is an American Multinational corporation, multinational computer technology company headquartered in Austin, Texas. Co-founded in 1977 in Santa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Corporation
Oracle Corporation is an American Multinational corporation, multinational computer technology company headquartered in Austin, Texas. Co-founded in 1977 in Santa Clara, California, by Larry Ellison, who remains executive chairman, Oracle was the List of the largest software companies, third-largest software company in the world in 2020 by revenue and market capitalization. The company's 2023 ranking in the Forbes Global 2000, ''Forbes'' Global 2000 was 80. The company sells Database, database software, particularly Oracle Database, and cloud computing. Oracle's core application software is a suite of enterprise software products, such as enterprise resource planning (ERP) software, human capital management (HCM) software, customer relationship management (CRM) software, enterprise performance management (EPM) software, Customer Experience Commerce (CX Commerce) and supply chain management (SCM) software. History Larry Ellison, Bob Miner, and Ed Oates co-founded Oracle in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tablespace
A tablespace is a storage location where the actual data underlying database objects can be kept. It provides a layer of abstraction between physical and logical data, and serves to allocate storage for all DBMS managed segments. (A database segment is a database object which occupies physical space such as table data and indexes.) Once created, a tablespace can be referred to by name when creating database segments. Overview Tablespaces specify only the database storage locations, not the logical database structure, or database schema. For instance, different objects in the same schema may have different underlying tablespaces. Similarly, a tablespace may service segments for more than one schema. Sometimes it can be used to specify schema so as to form a bond between logical and physical data. By using tablespaces, an administrator also can control the disk layout of an installation. A common use of tablespaces is to optimize performance. For example, a heavily used inde ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
RDBMS
A relational database (RDB) is a database based on the relational model of data, as proposed by E. F. Codd in 1970. A Relational Database Management System (RDBMS) is a type of database management system that stores data in a structured format using rows and columns. Many relational database systems are equipped with the option of using SQL (Structured Query Language) for querying and updating the database. History The concept of relational database was defined by E. F. Codd at IBM in 1970. Codd introduced the term ''relational'' in his research paper "A Relational Model of Data for Large Shared Data Banks". In this paper and later papers, he defined what he meant by ''relation''. One well-known definition of what constitutes a relational database system is composed of Codd's 12 rules. However, no commercial implementations of the relational model conform to all of Codd's rules, so the term has gradually come to describe a broader class of database systems, which at a minim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Data Recovery
In computing, data recovery is a process of retrieving deleted, inaccessible, lost, corrupted, damaged, overwritten or formatted data from computer data storage#Secondary storage, secondary storage, removable media or Computer file, files, when the data stored in them cannot be accessed in a usual way. The data is most often salvaged from storage media such as internal or external hard disk drives (HDDs), solid-state drives (SSDs), USB flash drives, Magnetic-tape data storage, magnetic tapes, Compact disc, CDs, DVDs, RAID subsystems, and other electronics, electronic devices. Recovery may be required due to physical damage to the storage devices or logical damage to the file system that prevents it from being Mount (computing), mounted by the host operating system (OS). Logical failures occur when the hard drive devices are functional but the user or automated-OS cannot retrieve or access data stored on them. Logical failures can occur due to corruption of the engineering chip, l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oracle Data Guard
The software which Oracle Corporation markets as Oracle Data Guard forms an extension to the Oracle relational database management system (RDBMS). It aids in establishing and maintaining secondary standby databases as alternative/supplementary repositories to production primary databases. Oracle provides both graphical user interface (GUI) and command-line (CLI) tools for managing Data Guard configurations. Data Guard supports both physical standby and logical standby sites. Oracle Corporation makes Data Guard available only as a bundled feature included within its "Enterprise Edition" of the Oracle RDBMS. With appropriately set-up Data Guard operations, DBAs can facilitate failovers or switchovers to alternative hosts in the same or alternative locations. Configurations For the purposes of Data Guard, each Oracle database functions either in a primary database role or in a standby database role - with the ability to transition from one role to the other. Physical standb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
