Imisebenzi esemqoka ye-DBMS

Modern semininingwane izinhlelo esetshenziswa ezintweni eziningi, kodwa hhayi wonke umuntu uyazi ukuthi ziyini lezo zinto nokuthi ungasebenzisa semininingwane imisebenzi. Lezi amathuluzi lenqwaba amathuba, ngakho kuzomele uqonde ukuthi bangakwenza futhi yini ewusizo umsebenzisi ukusebenzisa ngokugcwele kubo.

ukuphathwa idatha

Endaweni yokuqala, imisebenzi semininingwane zihlanganisa ukucutshungulwa kolwazi kwimemori yangaphandle, futhi lo msebenzi, yilungiselelo izakhiwo eziyisisekelo EP, okuyinto kudingeka singagcini nje ngokuzuza nokugcina imininingwane ngqo kufakwe egciniwe kodwa futhi ukwenza imisebenzi ehlukahlukene ehhovisi, ezifana nokuthola okusheshayo ukufinyelela kunoma yimaphi amafayela ezenzakalweni ezihlukahlukene. Ngo embodiments ezithile, ngenkuthalo esetshenziswa kungenzeka izinhlelo ezahlukene ifayela, kuyilapho abanye ahlinzeke umsebenzi, ngisho ezingeni inkumbulo kumadivayisi angaphandle. Kodwa kulokhu kuyafaneleka ukuthi imisebenzi egciniwe, ngezinga eliphezulu yentuthuko, umsebenzisi, noma kunjalo, akuyona ukwaziswa ukuthi yiluphi uhlelo isetshenziswa, futhi uma kunjalo, kanjani ukuhlela amafayela. Ikakhulukazi, uhlelo ubelokhu ebasekela oda lalo ukwetha izinto afakwe database.

RAM ukuphathwa sesikhashana

Ngo iningi labantu amacala umsebenzi semininingwane kuvamile ukusebenzisa yolwazi sasivumela voluminous futhi ubukhulu obuncane RAM ngokuvamile itholakala okuningi. Yiqiniso, uma endabeni yokwelashwa sento idatha ngamunye uzobe benana imemori yangaphandle, isivinini yokugcina oyosisiza ijubane uhlelo, ngakho cishe inketho yangempela kuphela ukwandisa idatha yayo kokubhafa e RAM. Kulokhu, ngisho noma uhlelo lokusebenza ihlinzeka sesikhashana zesistimu ebanzi, isibonelo Unix, le ngeke anele okuqinisekisa ukuthi database inhloso esemqoka imisebenzi, njengoba has a umthamo olukhudlwana idatha kwi izakhiwo ezuzisayo kokubhafa ngayinye ethile database esetshenziswa. Ngenxa yalesi uhlelo lokuthuthukiswa ukusekela awayo isebenza, kanye isiyalo esiyingqayizivele esikhundleni sabo.

Kuyaphawuleka yokuthi kukhona oseceleni lokulawula izinhlelo, sigxile khona okuqhubekayo ezisenkumbulweni lonke database. Lokhu isiqondiso kusekelwe ngoba kucatshangwa ukuthi esikhathini esizayo esiseduze inani RAM kukhompyutha yakho uzokwazi ukwandisa ukuze ngeke zisaba kwanoma iyiphi ukukhathazeka kokubhafa, futhi imisebenzi eyisisekelo lolu hlobo semininingwane lapha ziyowa nje isikhathi. Okwamanje, yonke le misebenzi zisengaphansi esigabeni sokuhlola.

ukuphathwa kuthengiselana

Wokuthengiselana ukulandelana kwemisebenzi ukusetshenziswa data base ukuphathwa isistimu ukuthi amaphi ephatha njengoba yomkhakha owodwa. Uma okwenziwayo ababulawa ngokugcwele ngempumelelo, uhlelo ithumba izinguquko eziye zashiwo ke, kwimemori wangaphandle noma ayikho lezi zinguquko angeke ibonakale isimo egciniwe. Lo msebenzi iyadingeka ukuze kusekelwe ubuqotho okunomqondo database esetshenziswa. Kufanele kuqashelwe ukuthi ukugcinwa inkambo efanele mshini kuthengiselana kungokudingekayo ngisho nalapho esebenzisa database olulodwa-yomsebenzisi, injongo kanye umsebenzi okuyinto zihluke ngokuphelele olimini ezinye izinhlobo izinhlelo.

Izakhiwo kunoma imuphi umsebenzi uqala ngalesi uhambisane nesimo semininingwane futhi ngaleyo ndlela awuyeka esimweni esifanayo ngemva kokuphela inqubo, okwenza kube lula kakhulu ukusebenzisa njengoba iyunithi umsebenzi ku-database. Nge Ukuphathwa ngendlela efaneleko ukuthenga ababulawa ngokulinganisa uhlelo ukulawula ngamunye umsebenzisi ngamunye, isimiso, ungaziqhenya yingxenye yalo lonke. Nokho, lokhu ngandlela-thile i ukumelwa ephelele yengxoxo, njengoba ezimweni eziningi lapho abantu besebenza namanje siyozwa khona ozakwabo uma ayesebenzisa inqubo multiuser, kodwa empeleni inikeza kakhulu umcabango we-database. Imisebenzi efana semininingwane multi-umsebenzisi futhi zihlotshaniswa imiqondo kuthengiselana ukuphathwa ezifana ukubulawa uhlelo serial, futhi serialization.

Yini zazisho ukuthini?

Serializing parallel kuthengiselana elisebenzisekayo kuhilela ukwakhiwa ekhethekile icebo labo, lapho umphumela Imininingwane izuzwe okulingana umphumela etholwe ingxube, ngenxa esahlulelweni ezilandelanayo.

ukukhishwa uhlelo yomkhiqizo isakhiwo eqondile isinyathelo, okuholela serialization. Yiqiniso, uma uhlelo etholwe ukunikeza ngempela Ukukhishwa serial ukuthengiselana ingxube ke yimuphi umsebenzisi ngubani elakhiwe kuthengiselana, makube khona abanye kuyoba ngokuphelele imperceptible, ngaphandle ukuthi izosebenza kancane kuqhathaniswa kwimodi olulodwa-umsebenzisi.

Kukhona ezinye eyisisekelo serialization algorithm. In izinhlelo eyodwa, ethandwa kakhulu namuhla ubuchule ukuthi zisekelwe ukuvumelanisa bamba ezahlukene izinto egciniwe. Endabeni iyiphi algorithm serialization inikeza ukuthi kungenzeka ukungqubuzana phakathi ukuthengiselana ezimbili noma ngaphezulu ukufinyelela izinto ezithile egciniwe. Esimweni esinjalo, ukusekela le nqubo, udinga ukubuyela emuva, okungukuthi, ukususa noma yimiphi izinguquko ezenziwe database ngokusebenzisa okukodwa noma ngaphezulu izinqubo. Lokhu nje ingenye izimo lapho uhlelo multi-yomsebenzisi, umuntu uzizwa khona abanye.

Ukungena ngemvume

Enye yezimfuneko zokusinda esiyinhloko izinhlelo zanamuhla ukuqinisekisa siyiqiniso Ulwazi isitoreji kwimemori bangaphandle. Ikakhulu, inikeza ukuthi omunye wemisebenzi eyinhloko database zihlanganisa ikhono alulame zokugcina isimo lovumelanako semininingwane ngemva okuvela kuyo noma iyiphi isofthiwe noma i-hardware ukwehluleka. Ngo iningi labantu amacala ayiswe cabanga ezimbili okukhethwa ukwehluleka hardware:

• elithambile, okungase esichazwa njengesono esiphambene stop ngokuzumayo siqoqelalwazi (Esadleni sakho kunjalo ezivamile - Emergency Amandla Off);
• eziqinile, izimpawu ukulahlekelwa esinqunyiwe noma ephelele idatha egcinwe kwimidiya yangaphandle.

Njengoba ukwehluleka isofthiwe Izibonelo eziphuthumayo uhlelo ukuvala shaqa uma uzama ukusebenzisa noma isiphi kungenzeka ukuthi omunye wemisebenzi eyinhloko a DBMS akufakwanga noma bamane batheleke noma iyiphi Umbuso umsebenzisi, lapho ukuthenga ezithile awukapheli. Isimo kokuqala kungase kubhekwe njengento okwakuvela ohlotsheni olukhethekile lwenkanyezi ukuhluleka okuthambile, kanti uma wale mithandazo kuyadingeka ukuze ayisuse imiphumela sokwenziwe olulodwa.

Yiqiniso, noma kunjalo ukutakula evamile semininingwane kuyadingeka ukuba ethile ulwazi olwengeziwe. Ngamanye amazwi, ukuze kugcinwe evamile ukuthembeka isitoreji idatha ku database kumelwe ukuqinisekisa komsebenzi kolwazi isitoreji, futhi ingxenye idatha isetshenziswa nokuvulwa kufanele kuqashelwe ngokucophelela. Indlela ejwayeleke kakhulu yokuqinisekisa nokugcinwa idatha eziphindaphindekayo, kubhekwa ngemvume izinguquko.

Kuyini futhi kanjani ukuyisebenzisa?

Umagazini iyingxenye ekhethekile database, okuyinto afinyelelwe eziningi semininingwane imisebenzi akufakiwe, futhi inakekelwa kahle. Kwezinye izimo, ngisho ngesikhathi esifanayo ke inikeza ukuxhasa amakhophi amabili magazini, ngaleso abezindaba ezahlukene ngokomzimba. Esikhathini esitolo wathola ulwazi mayelana nanoma yiziphi izinguquko ezenzeka engxenyeni eyinhloko database, futhi ezahlukene zokulawula zinguquko journaled emazingeni ehlukene. Kwezinye izimo, okufakile lwamakholi okuhambisana ngokugcwele ethile ukusebenza logic izinguquko, endaweni ethile - operation ubuncane yangaphakathi ehambisana ne-yangaphandle inkumbulo page ukuguqulwa, kuyilapho abanye DBMSs ezihilela ukusetshenziswa inhlanganisela izindlela ezimbili.

Kunoma yikuphi, lokho okubizwa ngokuthi "isu zokuqopha pre-emptive" kulo magazini. Ngo irekhodi isicelo yayo, kubonisa ushintsho iyiphi into semininingwane iwela inkumbulo sangaphandle umagazini phambi into onhlobonhlobo. Kuyaziwa ukuthi uma imisebenzi egciniwe Ukufinyelela zihlanganisa kokuhambisana evamile nale olandelwayo, kusetshenziswa umagazini ukuxazulula izinkinga ezihlobene yokutakula egciniwe uma kwenzeka noma yimuphi ukwehluleka.

ukufinyela

Isimo elula ukubuyiselwa kuthengiselana ngabanye is iphuma emuva. Ukuze le nqubo, akudingekile ukusebenzisa zesistimu ebanzi ushintsho lwamakholi, kwanele ukuyisebenzisa ukuze okwenziwayo ngamunye wendawo imisebenzi magazini ukuguqulwa, bese ukubuyela emuva kuthengiselana nge ngokufeza imisebenzi ephambene, kusukela ekupheleni irekhodi ngayinye. Isakhiwo umsebenzi semininingwane ngokuvamile kuhilela ukusetshenziswa nje isakhiwo esinjalo, kodwa ezimweni eziningi amalogi bendawo namanje ayisekelwa, futhi buyisela emuva ngisho ngazinye ukuthengiselana ngabanye eyenziwa ngumuntu zesistimu ebanzi, futhi ukuthi zonke amarekhodi okwenziwayo ngamunye ehlangene uhlu reverse.

Esimeni memory egciniwe yangaphandle ukwehluleka ezithambile kungafaka izinto ezihlukahlukene okuye kwashintshwa kwafakwa ngu ukuthengiselana akuphelelanga ngesikhathi nesenzakalo ukwehluleka, futhi kungase kube khona izinto ezahlukene, labo ethuthukisiwe eyaphothulwa ngempumelelo ngaphambi iphutha ngokusebenzisa okuqukethwe RAM sesikhashana okuyinto ubalekela ngokuphelele lapho kukhona izinkinga ezifanayo. Uma Iziphakamiso eziyisisekelo kuhambisana, ukuhlinzeka i-ukusetshenziswa namajenali zendawo ngempela ukubhala kwimemori bangaphandle, ezihlobene ukushintshwa noma yiziphi izinto ezinjalo.

Injongo eyinhloko inqubo emumva okuvela ukwehluleka ezithambile iyisimo kwimemori bangaphandle database main, okuyinto kwakuyovela esimweni ukulungisa ku-EAP yiziphi izinguquko yenkokhelo igcwaliswe futhi ngaleyo ndlela ngeke aqukethe iminonjana izinqubo akuphelele. Ukuze kuzuzwe lokhu Empeleni, ezinkulu semininingwane imisebenzi kuleli cala, buyisela ukuthengiselana uncommitted, obukwenza, imiphumela okwagcina ngeke uvele kwimemori bangaphandle. Lokhu kuhilela impela eningi ubuqili, okuyinto ikakhulukazi ezihlobana ngayo inhlangano ukuphathwa lalo magazini kanye isebenza.

ukwehluleka Hard

Uma kudingeka, ukubuyisela semininingwane emva nesenzakalo sokwehluleka kanzima iwumagazini hhayi kuphela, kodwa futhi isipele semininingwane. Lesi sakamuva ikhophi ephelele database ngaleso sikhathi njengoba umagazini aqala ukugcwala. Yiqiniso, ukuze inqubo yokutakula evamile kudinga ukuphepha magazini, Ngakho-ke, njengoba kushiwo ngaphambili, ukuze ukulondolozwa kwalo imemori yangaphandle eziphoqelelwe izidingo esiqinile kakhulu. Kulokhu, nokuvulwa database wukuthi, esekelwe amakhophi ezigciniwe of umagazini odlalwa yonke imisebenzi olwenziwa igcwaliswe ngesikhathi inhlekelele. Uma kudingeka, kungase ngisho idlalwe emsebenzini ukuthengiselana akuphelele futhi aqhubeka nomsebenzi wawo evamile ngemuva kokuphela inqubo yokutakula, kodwa izinhlelo iningi langempela, inqubo esinjalo kwenziwe ngenxa yokuthi ngokwako emumva ukwehluleka kanzima yinqubo kuqhathaniswa eside.

Ukusekela ulimi

Ukuze usebenze nge yolwazi zanamuhla zisebenzisa izilimi ezihlukahlukene, futhi database ekuseni, aphoyintimenti, imisebenzi kanye nezinye izici okuyinto zihluke ngokuphelele olimini uhlelo yesimanje nokulekelela ezikhethekile izilimi eziningi. Lawa kwakungamadodana ikakhulu SDL futhi DML, okuhloswe ukuchaza database schema kanye idatha ukuxhaphaza ngokulandelana.

SDL isetshenziswa ukuchaza isakhiwo okunomqondo database, okungukuthi, ukuba aqaphele isakhiwo eqondile database, elitholakala kubasebenzisi. DML sihlanganisa iqoqo opharetha zokukhwabanisa kolwazi, ikuvumela ukugcina ulwazi egciniwe, kanye susa, shintsha noma zisebenzisa idatha ekhona.

izici DBMS zihlanganisa izinhlobo ezahlukene ukwesekwa ulimi olulodwa oludidiyelwe enikezela zonke izinto ezidingekayo ukuze operation evamile yolwazi, kusukela ekudalweni yayo sokuqala, futhi inikeza interface yomsebenzisi ejwayelekile. Izinga ulimi enikeza imisebenzi eyisisekelo database okuvame kakhulu ezinsukwini yethu izinhlelo zingubudlelwane esetshenziswa SQL.

Kuyini lokhu?

Endaweni yokuqala ulimi ihlanganisa imisebenzi eyisisekelo DML futhi SDL, okungukuthi, inikeza kungenzeka ekunqumeni engasho lutho ethize database zingubudlelwane , kanye nekucinisa imininingwane edingekayo. Ngakho ezahlukene izinto yokuqamba semininingwane asekelwe ngqo lelulwimi ngomqondo wokuthi ukuguqulwa olwenziwe yesakhi amagama into e izikhombi yabo yangaphakathi, esekelwe asekelwe inkonzo amatafula ngokukhethekile-Izincwajana. Umnyombo uhlelo lokulawula, isimiso, akusho uxhumana amathebula noma amakholomu ngabanye.

Ulimi SQL sibandakanya uhla amathuluzi akhethekile ukuchaza semininingwane izingqinamba. Nalapha futhi, yimuphi imingcele enjalo zifakwe amatafula ekhethekile, izinhlu, kanye nokuqapha ubuqotho Kwenziwa ngqo ezingeni ngokolimi, okungukuthi ku inqubo kokufunda ngabanye izitatimende semininingwane ukuguqulwa yesakhi, esekelwe etholakala database ubuqotho izingqinamba, uchitha ukukhiqiza ikhodi ehambisana.