柿子树简笔画图片大全:In-memory database

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 in-memory database (IMDB; also main memory database system or MMDB) is a database management system that primarily relies on main memory for computer data storage. It is contrasted with database management systems which employ a disk storage mechanism. Main memory databases are faster than disk-optimized databases since the internal optimization algorithms are simpler and execute fewer CPU instructions. Accessing data in memory reduces the I/O reading activity when querying the data which provides faster and more predictable performance than disk. In applications where response time is critical, such as telecommunications network equipment and mobile ads networks, main memory databases are often used.[1]

Contents

  [hide] 
  • 1 ACID support
  • 2 "Hybrid" in-memory/on-disk databases
  • 3 Commercial products
  • 4 Products
  • 5 References
  • 6 See also
  • 7 External links

[edit]ACID support

In their simplest form, main memory databases store data on volatile memory devices. These devices lose all stored information when the device loses power or is reset. In this case, MMDBs can be said to lack support for the durability portion of the ACID (atomicity, consistency, isolation, durability) properties. Volatile memory-based MMDBs can, and often do, support the other three ACID properties of atomicity, consistency and isolation.

Many MMDBs add durability via the following mechanisms:

  • Snapshot files, or, checkpoint images, which record the state of the database at a given moment in time. These are typically generated periodically, or, at least when the MMDB does a controlled shut-down. While they give a measure of persistence to the data (in that not everything is lost in the case of a system crash) they only offer partial durability (as 'recent' changes will be lost). For full durability, they will need to be supplemented by one of the following:
  • Transaction logging, which records changes to the database in a journal file and facilitates automatic recovery of an in-memory database.
  • Non-volatile random access memory (NVRAM), usually in the form of static RAM backed up with battery power (battery RAM), or an electrically erasable programmable ROM (EEPROM). With this storage, the MMDB system can recover the data store from its last consistent state upon reboot.
  • High availability implementations that rely on database replication, with automatic failover to an identical standby database in the event of primary database failure. To protect against loss of data in the case of a complete system crash, replication of a MMDB is normally used in conjunction with one or more of the mechanisms listed above.

Some MMDBs allow the database schema to specify different durability requirements for selected areas of the database - thus, faster-changing data that can easily be regenerated or that has no meaning after a system shut-down would not need to be journaled for durability (though it would have to be replicated for high availability), whereas configuration information would be flagged as needing preservation.


"Hybrid" in-memory/on-disk databases

The first database engine to support both in-memory and on-disk tables in a single database was released in 2003.[2] The advantage to this approach is flexibility: the developer can strike a balance between performance (which is enhanced by sorting, storing and retrieving specified data entirely in memory, rather than going to disk); cost, because a less expensive hard disk can be substituted for more memory; persistence; and form factor, because RAM chips cannot approach the density of a small hard drive.

Manufacturing efficiency is another reason a combined in-memory/on-disk database system may be chosen. Some device product lines, especially in consumer electronics, include some units with permanent storage, and others that rely on memory for storage (set-top boxes, for example). If such devices require a database system, a manufacturer can adopt a hybrid database system at lower cost, and with less code customization, than using separate in-memory and on-disk databases, respectively, for its disk-less and disk-based products.


Commercial products

Research in main-memory database systems started around 1993 at Bell Labs. It was prototyped as the Dali Main-Memory Storage Manager.[3] This research lead to first commercial main-memory database, Datablitz. In recent years, main memory databases have attracted the interest of larger database vendors. TimesTen, a start-up company founded by Marie-Anne Neimat in 1996 as a spin-off from Hewlett-Packard, was acquired by Oracle Corporation in 2005. Oracle now markets this product as both a standalone database and an in-memory database cache to the Oracle database. IBM acquired SolidDB in 2008, and Microsoft is widely rumored to be launching an in-memory solution in 2009.[4] SAP announced general availability of SAP HANA in June 2011.


Products

Product nameLicenseDescriptionAdaptive Server Enterprise (ASE) 15.5Proprietaryenterprise database from Sybase)[5]Apache DerbyApache License 2.0Java RDBMSAltibaseProprietaryhas in-memory and disk table; HYBRID DBMSBlackRayGNU General Public Licence (GPLv2) and BSD LicenseCSQLGNU General Public Licence or proprietaryDatablitzProprietaryDBMSEloqueraProprietaryIn-memory, In-memory:persist modeseXtremeDBcommercial productDBMS, also check out its open source PERST dbms.Finances Without Problemscommercial productprimarily in-memory database with hybrid featuresFleetDBMITNOSQL db with Writing to an append-only log to provide durability.H2Mozilla Public License or Eclipse Public Licensehas a memory-only modeHSQLDBBSD licensehas a memory-only modeIBM TM1Proprietaryin-memory BI and data analysisInfoZoomProprietaryin-memory BI and data analysisKDBProprietaryDBMS, also supports disk based data#liveDBOpen SourcePrevalence enginemembaseApache LicenseNoSQL, hybridMercuryProprietaryobject oriented, in-memory data management with persistency support, in-built compiler, hosts application server on same machine; developed by staila technologies, an ETHZ spinoff [6]MicroStrategyin-memory BI for MicroStrategy 9MonetDBMonetDB LicenseMySQLGNU General Public License or proprietaryhas a cluster server which uses a main-memory storage engineOracle Berkeley DBSleepycat Licensecan be configured to run in memory onlyPanoramafor Windows and Macintosh, both single user and server versionsParAccelProprietaryin-memory, columnar, relational, ACID-compliant; disk-based mode as wellPolyhedra IMDBProprietaryrelational, supports High-Availability; acquired in 2001 by ENEAQlikViewBI-tool developed by QlikTechRDM EmbeddedProprietaryincluding hybridRDM ServerProprietaryincluding hybridRedisBSDNoSQLsolidDB by IBMincluding hybrid, HSB-based HA, Shared memory, embedded, XA, etc.SAP HANA databaseProprietaryDatabase engine of the SAP In-Memory Appliance (SAP HANA) produced by SAP AGSQLitePublic domainhybrid, RAM and disk dbs can be used togetherStarcounterin-memory object relational dbmsTarantoolBSDNoSQL, extendable with Lua stored proceduresTimesTen by Oraclein memory only or as a cache for Oracle DatabaseVertipaqProprietaryMicrosoft PowerPivot and Microsoft Analysis Services in-memory BI engineVoltDBGNU General Public License v3in-memoryTREXsearch engine in the SAP NetWeaver integrated technology platform produced by SAP AGXcelerix by Frontexcommercial productWX2 by Kognitiocommercial productXeroundcommercial product, database as a service, in-memory infrastructure with MySQL front-end


References

  1. ^ "TeleCommunication Systems Signs up as a Reseller of TimesTen; Mobile Operators and Carriers Gain Real-Time Platform for Location-Based Services". Business Wire. 2002-06-24.
  2. ^ "Solid Announces General Availability of BoostEngine 4.0, the First On-Disk/In-Memory Hybrid Database Manager" (Press release). PR Newswire. 2003-04-28.
  3. ^ [1]
  4. ^ http://www.intelligententerprise.com/channels/business_intelligence/showArticle.jhtml?articleID=210700171
  5. ^ http://www.sybase.com/products/databasemanagement/adaptiveserverenterprise
  6. ^ http://www.vpf.ethz.ch/transfer/firmgruend/spinoff_list/overview
  • Jack Belzer. Encyclopedia of Computer Science and Technology - Volume 14: Very Large Data Base Systems to Zero-Memory and Markov Information Source. Marcel Dekker Inc.ISBN 0-8247-2214-0.


See also in Memory Data Grid - In Memory Distributed Data management

  • Embedded Databases
  • NoSQL - Alternative Scale-out Databases


External links

  • SAP HANA Now Generally Available to Customers Worldwide
  • In-Memory Database Systems Questions and Answers
  • IBM Systems and Services for SAP HANA
  • SolidDB and the secrets of speed - How the IBM in-memory database redefines high performance
  • Oracle TimesTen in-memory database
  • The Rebirth of the In-Memory Database
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