Kusho ukuthini uma i-database ihambisana ne-ACID?
Context:Ku-computer science, i-ACID (i-atomicity, ukuvumelana, ukuhlukaniswa, ukuqina) iqoqo lezakhiwo zokuthengiselana kwedatha okuhloswe ngakho ukuqinisekisa ukuba semthethweni kwedatha naphezu kwamaphutha, ukwehluleka kwamandla, nezinye izingozi. Ngokuphathelene nemininingwane yolwazi, ukulandelana kwemisebenzi yolwazi eyanelisa izakhiwo ze-ACID (engabhekwa njengokusebenza okukodwa okunengqondo kwedatha) kubizwa ngokuthi ukuthengiselana. Ngokwesibonelo, ukudluliselwa kwemali kusuka kwelinye i-akhawunti yasebhange kuya kwelinye, ngisho noma kuhilela izinguquko eziningi njengokukhokhisa i-akhawunti eyodwa nokukhokhisa enye, kungukuthengiselana okukodwa.  Ngo-1983, u-Andreas Reuter noTheo Härder basungula isifinyezo se-ACID, bakha ngomsebenzi wangaphambilini kaJim Gray owaqamba i-atomicity, ukuvumelana, nokuqina, kodwa hhayi ukuhlukaniswa, lapho kuchaza umqondo wokuthengiselana. Lezi zici ezine ziyiziqinisekiso ezinkulu ze-paradigm yokuthengiselana, eye yathonya izici eziningi zokuthuthukiswa kwezinhlelo ze-database.  Ngokusho kukaGray noReuter, i-IBM Information Management System yayisekela ukuthengiselana kwe-ACID ekuqaleni kuka-1973 (yize isifinyezo sakhiwa kamuva).  I-Atomicity noma i-atomicity Isihloko esiyinhloko: I-Atomicity (izinhlelo zedatha) Ngokuvamile ukuthengiselana kwakhiwa izitatimende eziningi. I-Atomicity iqinisekisa ukuthi ukuthengiselana ngakunye kubhekwa "njengeyunithi" eyodwa, ephumelela ngokuphelele noma ehluleka ngokuphelele: uma noma yimiphi imibiko ehlanganisa ukuthengiselana ihluleka ukuqedela, konke ukuthengiselana kuhluleka futhi i-database ishiywe ingashintshiwe. Uhlelo lwe-athomu kumelwe luqinisekise ukuba yi-athomu kuzo zonke izimo, kuhlanganise nokwehluleka kukagesi, amaphutha, nokuphahlazeka. Isiqinisekiso se-atomicity sivimbela ukubuyekezwa kwesisekelo semininingwane ukuba kwenzeke kuphela ngokwengxenye, okungabangela izinkinga ezinkulu kunokwenqaba lonke uchungechunge ngokuphelele. Ngenxa yalokho, ukuthengiselana akukwazi ukubonwa ukuthi kuyaqhubeka ngomunye umthengi wedatha. Ngesinye isikhathi, akukaze kwenzeke, futhi ngokulandelayo, sekuvele kwenzeke ngokuphelele (noma akwenzekanga lutho uma ukuthengiselana kukhanseliwe kuqhubeka).  Ukuvumelana Isihloko esiyinhloko: Ukuvumelana (izinhlelo ze-database) Ukuvumelana kuqinisekisa ukuthi ukuthengiselana kungaletha kuphela i-database kusuka kwesinye isimo esivumelana nesinye, kulondolozwe ukungaguquguquki kwe-database: noma iyiphi idatha ebhalwe ku-database kumele isebenze ngokuya ngayo yonke imithetho echaziwe, kufaka phakathi imikhawulo, ama-cascades, ama-trigger, nanoma iyiphi inhlanganisela yawo. Lokhu kuvimbela ukonakala kwedatha ngokuthengiselana okungekho emthethweni. Ubuqotho bokubhekisela buqinisekisa ubudlelwano bomkhombandlela oyinhloko nomkhombandlela wangaphandle.  Ukuhlukaniswa Isihloko esiyinhloko: Isolation (database systems) Ukuthengiselana kuvame ukwenziwa ngesikhathi esisodwa (isib., ukuthengiselana okuningi okufundwayo nokubhalwa etafuleni ngesikhathi esisodwa). Ukuhlukaniswa kuqinisekisa ukuthi ukwenziwa okuhambisanayo kokuthengiselana kushiya i-database isesimweni esifanayo ebesingatholakala uma ukuthengiselana bekwenziwa ngokulandelana. Ukuhlukaniswa kuyinjongo eyinhloko yokulawulwa kokuhambisana; kuye ngokuthi izinga lokuhlukaniswa elisetshenzisiwe, imiphumela yokuthengiselana okungaphelele ingase ingabonakali kwezinye izinkokhelo.  Ukuqina Isihloko esiyinhloko: Ukuhlala isikhathi eside (izinhlelo ze-database) Ukuhlala isikhathi eside kuqinisekisa ukuthi uma isivumelwano sesibophezelekile, sizohlala sibophezelekile ngisho noma kunenkinga yesistimu (isibonelo, ukuphazamiseka kwamandla noma ukuphahlazeka). Lokhu ngokuvamile kusho ukuthi ukuthengiselana okuqediwe (noma imiphumela yako) kuqoshwa enkumbulweni engaguquki.
I - ACID isifinyezo esisho ukuthi Atomicity, Consistency, Isolation, and Durability. I-atomicity isho ukuthi izenzo zenzeka ngokuphelele noma cha; akukho ukubhala okuyingxenye noma isimo lapho ingxenye yesenzo kuphela eqediwe. Ukuze uthole i-database, lokhu kusho ukuthi uma idatha ibhaliwe ekuthengiselaneni okukodwa, lokho kuthengiselana kupheleliswa ngokuphelele noma kuhluleke ngokuphelele ngaphandle kwedatha eshiywe ngemuva esimweni esiyingxenye noma esonakele. Ukuvumelana kusho ukuthi ukuthengiselana kuthatha isimo sisuka kwesinye isimo esisemthethweni siye kwesinye isimo esisemthethweni, ngaphandle kwendlela yokungena esimweni esingekho emthethweni. Ukuhlukaniswa kusho ukuthi abafundi/abalobi abaningi ku-database efanayo abaphazamisi omunye nomunye futhi bangaqhubeka ngaphandle kokukhathazeka ngemiphumela yesinye isenzo esenzekayo. Ukuhlala isikhathi eside kusho ukuthi isimo sigcinwa naphezu kokuhluleka nokuvala, isibonelo, leso simo sihlala sigcinwe kuze kube phakade.