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BerkeleyDB
Berkeley DB (BDB) is an unmaintained embedded database software library for key/value data, historically significant in open source software. Berkeley DB is written in C with API bindings for many other programming languages. BDB stores arbitrary key/data pairs as byte arrays, and supports multiple data items for a single key. Berkeley DB is not a relational database, although it has advanced database features including database transactions, multiversion concurrency control and write-ahead logging. BDB runs on a wide variety of operating systems including most Unix-like and Windows systems, and real-time operating systems. BDB was commercially supported and developed by Sleepycat Software from 1996 to 2006. Sleepycat Software was acquired by Oracle Corporation in February 2006, who continued to develop and sell the C Berkeley DB library. In 2013 Oracle re-licensed BDB under the AGPL license. As of 2022 Oracle has ceased to develop BDB. Bloomberg LP continues to develop a for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Margo Seltzer
Margo Ilene Seltzer is a professor and researcher in computer systems. She is currently the Canada 150 Research Chair in Computer Systems and the Cheriton Family Chair in Computer Science at the University of British Columbia. Previously, Seltzer was the Herchel Smith Professor of Computer Science at Harvard University's John A. Paulson School of Engineering and Applied Sciences and director at the Center for Research on Computation and Society. Education Seltzer received her A.B. in Applied Mathematics at Harvard/ Radcliffe College in 1983, where she was teaching assistant under Harry R. Lewis at Harvard University. In 1992, she received her Ph.D. in Computer Science from the University of California, Berkeley where her dissertation, "File System Performance and Transaction Support", was supervised by Michael Stonebraker. Her work in log-structured file systems, databases, and wide-scale caching is especially well-known, and she was lead author of the BSD-LFS paper. Caree ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Key–value Database
A key–value database, or key–value store, is a data storage paradigm designed for storing, retrieving, and managing associative arrays, and a data structure more commonly known today as a ''dictionary'' or ''hash table''. Dictionaries contain a collection of ''objects'', or ''records'', which in turn have many different ''fields'' within them, each containing data. These records are stored and retrieved using a ''key'' that uniquely identifies the record, and is used to find the data within the database. Key–value databases work in a very different fashion from the better known relational databases (RDB). RDBs predefine the data structure in the database as a series of tables containing fields with well defined data types. Exposing the data types to the database program allows it to apply a number of optimizations. In contrast, key–value systems treat the data as a single opaque collection, which may have different fields for every record. This offers considerable flexib ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Comdb2
Comdb2 is an open source, highly available clustered RDBMS developed by Bloomberg LP, built on optimistic concurrency control techniques. It provides multiple isolation levels, including Snapshot and Serializable Isolation. Read/Write transactions run on any node, with the client library transparently negotiating connections to lowest cost (latency) node which is available. Comdb2 implements queues for publisher-to-subscriber message delivery. Queues can be combined with table triggers for time-consistent log distribution. Comdb2 supports the SQLite dialect of SQL with some modifications, and embeds the Lua scripting language. Comdb2 maintains a fork of Berkeley DB to provide the key–value database backend to SQLite. Comdb2 architecture was described in detail in 2016 technical paper.http://www.vldb.org/pvldb/vol9/p1377-scotti.pdf See also * Comparison of relational database management systems * Multi-master replication Multi-master replication is a method of databas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fork (software Development)
In software engineering, a project fork happens when developers take a copy of source code from one software package and start independent development on it, creating a distinct and separate piece of software. The term often implies not merely a development branch, but also a split in the developer community; as such, it is a form of schism. Grounds for forking are varying user preferences and stagnated or discontinued development of the original software. Free and open-source software is that which, by definition, may be forked from the original development team without prior permission, and without violating copyright law. However, licensed forks of proprietary software (''e.g.'' Unix) also happen. Etymology The word "fork" has been used to mean "to divide in branches, go separate ways" as early as the 14th century. In the software environment, the word evokes the fork system call, which causes a running process to split itself into two (almost) identical copies that (ty ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bloomberg L
Bloomberg may refer to: People * Daniel J. Bloomberg (1905–1984), audio engineer * Georgina Bloomberg (born 1983), professional equestrian * Michael Bloomberg (born 1942), American businessman and founder of Bloomberg L.P.; politician and mayor of New York City (2002–2013) * Ramon Bloomberg (born 1972), American artist and film director Other uses * Bloomberg L.P., financial news and media company founded by Michael Bloomberg ** Bloomberg News, a news agency ** ''Bloomberg Businessweek'', weekly business magazine and website ** ''Bloomberg Markets,'' a monthly financial magazine ** Bloomberg Radio, a business radio network ** Bloomberg Television, a business news channel ***Bloomberg TV Canada ***Bloomberg TV Philippines ***Bloomberg TV Malaysia ** Bloomberg Terminal, desktop terminal and software widely used in the financial industry ** Bloomberg Data, API product using sftp or web service protocols to retrieve market data ** Bloomberg Government, online news service c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Linux Weekly News
LWN.net is a computing webzine with an emphasis on free software and software for Linux and other Unix-like operating systems. It consists of a weekly issue, separate stories which are published most days, and threaded discussion attached to every story. Most news published daily are short summaries of articles published elsewhere, and are free to all viewers. Original articles are usually published weekly on Thursdays and are available only to subscribers for two weeks, after which they become free as well. LWN.net is part of Eklektix, Inc. LWN caters to a more technical audience than other Linux/free software publications. It is often praised for its in-depth coverage of Linux kernel internals and Linux kernel mailing list (LKML) discussions. The acronym "LWN" originally stood for ''Linux Weekly News''; that name is no longer used because the site no longer covers exclusively Linux-related topics, and it has daily as well as weekly content. History Founded by Jonathan Corb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AGPL 3
The GNU Affero General Public License (GNU AGPL) is a free, copyleft license published by the Free Software Foundation in November 2007, and based on the GNU General Public License, version 3 and the Affero General Public License. The Free Software Foundation has recommended that the GNU AGPLv3 be considered for any software that will commonly be run over a network.List of free-software licences on the FSF website "''We recommend that developers consider using the GNU AGPL for any software which will commonly be run over a network.''" The Free Software Foundation explains the need for the license in the case when a free program is run on a server: The GNU Affero General Public License is a modified version of the ordinary GNU GPL version 3. It has one added requirement: if you ... |
Real-time Operating System
A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which manages the sharing of system resources with a scheduler, data buffers, or fixed task prioritization in a multitasking or multiprogramming environment. Processing time requirements need to be fully understood and bound rather than just kept as a minimum. All processing must occur within the defined constraints. Real-time operating systems are event-driven and preemptive, meaning the OS is capable of monitoring the relevant priority of competing tasks, and make changes to the task priority. Event-driven systems switch between tasks based on their priorities, while time-sharing systems switch the task based on clock interrupts. Characteristics A key characteristic of an RTOS is the level of its consistency concerning the amount of time it ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Operating System
An operating system (OS) is system software that manages computer hardware, software resources, and provides common services for computer programs. Time-sharing operating systems schedule tasks for efficient use of the system and may also include accounting software for cost allocation of processor time, mass storage, printing, and other resources. For hardware functions such as input and output and memory allocation, the operating system acts as an intermediary between programs and the computer hardware, although the application code is usually executed directly by the hardware and frequently makes system calls to an OS function or is interrupted by it. Operating systems are found on many devices that contain a computer from cellular phones and video game consoles to web servers and supercomputers. The dominant general-purpose personal computer operating system is Microsoft Windows with a market share of around 74.99%. macOS by Apple Inc. is in second place (14.84%), and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Write-ahead Logging
In computer science, write-ahead logging (WAL) is a family of techniques for providing atomicity and durability (two of the ACID properties) in database systems. A write ahead log is an append-only auxiliary disk-resident structure used for crash and transaction recovery. The changes are first recorded in the log, which must be written to stable storage, before the changes are written to the database. The main functionality of a write-ahead log can be summarized as: * Allow the page cache to buffer updates to disk-resident pages while ensuring durability semantics in the larger context of a database system. * Persist all operations on disk until the cached copies of pages affected by these operations are synchronized on disk. Every operation that modifies the database state has to be logged on disk before the contents on the associated pages can be modified * Allow lost in-memory changes to be reconstructed from the operation log in case of a crash. In a system using WAL, all mo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Multiversion Concurrency Control
Multiversion concurrency control (MCC or MVCC), is a 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 read-write lock. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 a database. Transactions in a database environment have two main purposes: # To provide reliable units of work that allow correct recovery from failures and keep a database consistent even in cases of system failure. For example: when execution prematurely and unexpectedly stops (completely or partially) in which case many operations upon a database remain uncompleted, with unclear status. # To provide isolation between programs accessing a database concurrently. If this isolation is not provided, the programs' outcomes are possibly erroneous. 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
