Babban ayyuka na DBMS

Modern database tsarin amfani da kan mutane da yawa abubuwa, amma ba kowa ya san abin da su ne da kuma yadda za ka iya amfani da database ayyuka. Wadannan kayan aikin ne mai babbar yawan yiwuwa, don haka ya kamata ka gane cewa ba za su iya yi da kuma abin da amfani ga mai amfani ga cikakken amfani da su.

data management

A farko wuri, a cikin database ayyuka sun hada da aiki na bayanai a waje memory, kuma wannan aiki ne da arziki na asali Tsarin daga cikin EP, wanda ake bukata ba kawai don kantin sayar da bayanai kai tsaye kunshe a cikin database amma kuma yin daban-daban ofishin ayyuka, kamar samun sauri samun wani fayiloli a lokuta daban-daban. A wasu embodiments, rayayye amfani da yiwuwar daban-daban fayil tsarin, yayin da wasu samar domin aikin, ko da a matakin waje ƙwaƙwalwar na'urorin. Amma a cikin wannan hali shi ne ya kamata a lura da cewa database ayyuka, tare da wani babban mataki na ci gaba, mai amfani, a cikin wani hali, ba a sanar da ko wani tsarin da ake amfani, kuma idan haka, yadda za a tsara fayiloli. A musamman, da tsarin da aka goyon bayan da kansa domin ambata sunayen da abubuwa kunshe a cikin database.

RAM buffer management

A mafi yawan lokuta da database aiki ne na kowa ya yi amfani da wani fairly voluminous databases da m size ne sau da yawa fiye da samuwa RAM. Hakika, idan a cikin hali na jiyya ga kowane data abu za a yi musayar tare da waje ƙwaƙwalwar, cikin sauri na karshen za su dace da gudun da tsarin, don haka kusan kawai real zaɓi ne don kara yawan buffering data a RAM. A wannan yanayin, ko da idan tsarin aiki na samar da wani tsarin-fadi da buffer, misali to UNIX, a wannan ba zai zama isa ya tabbatar da cewa database a cikin manufa da kuma babban ayyuka, kamar yadda yana da yawa ya fi girma girma na bayanai a kan m Properties na buffering kowane takamaiman ɓangare na database amfani. Saboda wannan ci gaban tsarin, don taimaka wa da kansa ya kafa buffers, kazalika da musamman horo su maye.

Shi ne ya kamata a lura da cewa akwai wani raba line na kula da tsarin, mayar da hankali a kan ci gaba da hallara a ƙwaƙwalwar na dukan database. Wannan shugabanci dogara ne a kan zato cewa a nan gaba cikin adadin RAM a kan kwamfutarka za a iya fadada haka da cewa ba za su ƙara zama na wani buffering damuwa, da kuma na asali ayyuka na irin wannan database a nan zai fada kawai a lokacin. A lokacin, dukan waɗannan ayyuka ne har yanzu a cikin gwaji lokaci.

ma'amala management

A ma'amala ne jerin ayyukan da amfani da data tushe management system wanda ya bi kamar guda mahaluži. Idan ma'amala da aka cikakken kashe nasarar, da tsarin kama da canje-canje da aka sanya da shi, a cikin external memory ko babu wani daga wadannan canje-canje ba za a nuna a kan jihar da database. Wannan aiki da ake bukata domin tallafawa ma'ana mutuncin database amfani. Ya kamata a lura da cewa goyon baya na daidai hanya na ma'amala inji ne kafin ko lokacin amfani da guda-mai amfani da database, da manufa da kuma aiki da abin da suke muhimmanci daban-daban daga sauran iri tsarin.

A dukiya da cewa wani fatauci fara kawai a wata m jihar database da haka ya bar shi a guda jihar bayan karshen hanya, yin shi musamman dace don amfani a matsayin naúrar na aiki a kan database. Tare da ta dace management na ma'amaloli an kashe a layi daya da kula da tsarin kowane mutum mai amfani, bisa manufa, za a iya jin ɓangare na dukan. Duk da haka, wannan shi ne a wasu hanya da wani idealized misali, kamar yadda a da yawa yanayi a lõkacin da aiki mutane har yanzu zai ji gaban takwarorinsa idan suka yi amfani da wani multiuser tsarin, amma a gaskiya shi na samar da sosai ra'ayi na database. Ayyuka kamar Multi-mai amfani da database ya ma aka hade da ma'amala management Concepts kamar serial kisa da shirin, da kuma serialization.

Shin me suke nufi?

Serializing layi daya executable ma'amala shafi na musamman shiri na aikin shirin, cikinsa da total sakamako cimma yake daidai da sakamakon samu cakuda, saboda su bi da bi kisa.

Serial kisa shirin ne a takamaiman tsarin mataki, wadda take kaiwa zuwa serialization. Hakika, idan da tsarin da aka samu don samar da wani gaske A serial kisan ma'amaloli cakuda, sa'an nan wani mai amfani wanda generated da fatauci, gaban wasu za su zama cikakken imperceptible, sai dai cewa ita za ta yi aiki a bit hankali idan aka kwatanta da guda-mai amfani mode.

Akwai wasu muhimman serialization algorithm. A centralized tsarin, mafi mashahuri a yau ne Algorithms cewa su ne bisa aiki tare kama daban-daban database abubuwa. A cikin hali na wani serialization algorithm azurta yiwuwar rikici tsakanin biyu ko fiye da ma'amaloli a kan samun wani database abubuwa. A irin wannan halin da ake ciki, don tallafa wa wannan hanya, kana bukatar ka mirgine baya, cewa shi ne, kawar da duk wani canje-canje sanya da database ta hanyar daya ko fiye tafiyar matakai. Wannan shi ne kawai daya daga cikin yanayi inda wani Multi-mai amfani da tsarin, daya ji gaban wasu.

gizo

Daya daga cikin manyan bukatun ga zamani tsarin ne don tabbatar da AMINCI bayanai ajiya a waje memory. A musamman, ta tanadi cewa daya daga cikin manyan ayyuka na database hada da ikon mai da na karshe jiwuwa jihar na database bayan da ya faru na wani software ko hardware gazawar. A mafi yawan lokuta dauka don la'akari da biyu zaɓuɓɓuka saboda hardware kasawa:

• taushi, wanda za a iya fassara a matsayin kwatsam tasha na kwamfutarka (fi na kowa hali - gaggawa Power Kashe).
• m, wanda aka halin da m ko cikakken asarar data adana a waje kafofin watsa labarai.

Kamar yadda software kasawa Misalai gaggawa tsarin kashewa a lokacin da kokarin amfani da duk wani yiwuwar cewa daya daga cikin manyan ayyuka na wani DBMS ba kunshe ko fadi wani mai amfani da mai amfani, inda wani fataucinsu bai yi ba aka kammala. A halin da ake ciki na farko iya dauke a matsayin na musamman irin taushi gazawar, yayin da a yanayin na karshen wajibi ne a kawar da sakamakon guda ma'amala.

Hakika, a wani hali ga al'ada database dawo da wajibi ne a yi wani adadin ƙarin bayani. A wasu kalmomin, ga al'ada kula da AMINCI data ajiya a cikin database dole ne ka tabbatar da redundancy na bayanai ajiya, da kuma wani ɓangare na bayanai da aka yi amfani da dawo da ya kamata a tsare a hankali. A mafi kowa Hanyar tabbatar da kiyaye m data, yana dauke da za a shiga canje-canje.

Mẽne ne da kuma yadda za a yi amfani da?

A mujallar ne na musamman da wani ɓangare na database, wanda aka isa a yawan database ayyuka ba su hada da, da kuma shi ne kiyaye sosai a hankali. A wasu yanayi, ko da a lokaci guda shi bayar da goyon baya ga biyu kofe na mujallar, a daban-daban jiki kafofin watsa labarai. A cikin kantin sayar da samu bayanai game da duk wani canje-canje da faruwa a cikin babban ɓangare na database, da kuma daban-daban kula da tsarin canje-canje iya journaled a matakai daban-daban. A wasu yanayi, wani log shigarwa ne cikakken m tare da da wani dabaru aiki canje-canje, wani wuri - wani m ciki aiki hade da waje memory page gyara, yayin da wasu DBMSs unsa da amfani mai hade da biyu fuskanci.

A cikin wani hali, wani da ake kira "dabarun na pre-emptive rikodi" a cikin mujallar. A aikace rikodin, ya nuna wani canji a cikin wani database abu da dama a cikin external memory na mujallar kafin m abu. An sani cewa idan ayyuka Access database hada al'ada da aiwatar da wannan yarjejeniya, ta amfani da mujallar don warware wasu matsaloli da suka shafi database dawo a taron na wani kasawa.

recoil

A halin da ake ciki sauki ne na maido da mutum ma'amala da aka yi birgima baya. Domin wannan hanya, ba lallai ba ne su yi amfani da tsarin-fadi da canji log, kuma shi ne isa ya yi amfani ga kowane ma'amala a gida mujallar gyara aiki, sa'an nan mirgine baya ma'amala da aiwatar da kishiya ake gudanar, fara daga ƙarshen kowane rikodin. A tsarin da database aiki sau da yawa shafi yin amfani da kawai irin wannan tsari, amma a mafi yawan lokuta cikin gida rajistan ayyukan har yanzu ba shi da tallafi, har ma mutum rollback na mutum ma'amaloli da za'ayi da wani tsarin-fadi, da kuma ga cewa duk records na kowane ma'amala hada baya jerin.

A taron na mai taushi gazawar waje database memory iya hada daban-daban abubuwa da aka modified da ma'amaloli ba kammala da lokacin da ya faru na rashin cin nasara, da kuma ma yana iya zama wani daban-daban abubuwa, da kyautata wadanda da aka samu nasarar kammala kafin Laifi ta yin amfani da RAM buffer abinda ke ciki wanda gaba daya vuya a lokacin akwai irin wannan matsaloli. Idan yarjejeniya da aka complied tare, samar da yin amfani da gida mujallolin suna dole rubuta a cikin external memory, wanda lãbãri zuwa gyare-gyare na wani irin abubuwa.

Babban manufar da dawo da tsarin bayan da ya faru na da taushi gazawar a jihar na waje memory na babban database, wanda zai bayyana a cikin hali na kayyade a cikin EaP wani canje-canje ga kammala ma'amala da haka ba dauke da burbushi na bai cika hanyoyin. Don cimma wannan sakamako, da babbar database ayyuka ne a cikin wannan harka, rollback uncommitted ma'amaloli, maimaita aiki, sakamakon abin da kyakkyawan ba zai bayyana a waje memory. Wannan tsari ya shafi quite mai yawa tausasãwa, wanda yafi dangantaka da kungiyar of management na mujallar kuma buffers.

Hard kasawa

Idan dole, mayar da database bayan da ya faru na tukuru kasawa ba kawai a mujallar, amma kuma a database madadin. A karshen ne cikakken kwafi na database a lokacin da mujallar ta fara cika. Hakika, na da wata al'ada dawo da hanya na bukatar a mujallar lafiya, saboda haka, kamar yadda aka ambata a baya, to ta adana a waje memory hõre sosai m bukatun. A wannan yanayin, dawo da database ne cewa, bisa Siyasa kofe na mujallar ana buga duk gudanar da ma'amaloli kammala a lokacin bala'i. Idan dole, zai iya ko da za a buga aikin bai cika ma'amaloli da kuma ci gaba da al'ada aiki bayan ƙarshen dawo da tsarin, amma a mafi real tsarin, irin wannan hanya ake ba da za'ayi domin dalilin cewa a kanta dawo bayan wuya maye ne mai gwada dogon hanya.

harshen Support

Don aiki tare da zamani databases amfani da harsuna daban daban, da kuma a cikin farkon database, alƙawari, ayyuka da kuma sauran halaye, wanda suke da muhimmanci daban-daban daga cikin na zamani tsarin samar da musamman goyon baya ga mahara harsuna. Waɗannan su ne yafi SDL da DML, aka yi nufi ga ayyana database tsari da kuma bayanan magudi, bi da bi.

SDL ake amfani da su ayyana ma'ana tsarin da database, da cewa shi ne, don gane takamaiman tsarin da database, wanda shi ne samuwa ga masu amfani. DML kuma ya hada da wani sa na aiki magudi da bayanai, ba ka damar adana bayanai a database, kazalika da share, gyara ko amfani da data kasance bayanai.

DBMS siffofin hada daban-daban na goyon bayan guda Hadakar harshen cewa samar ga dukkan albarkatun da ake bukata domin al'ada aiki na bayanai, daga ta farko halitta, da kuma bayar da wani misali mai amfani da ke dubawa. A misali harshen cewa samar da ainihin ayyuka na database ya fi na kowa a cikin kwanaki na da zumunci tsarin, amfani da SQL.

Mene ne wannan?

A farko wuri da harshen hadawa da asali ayyuka na DML da SDL, wato, na samar da yiwuwar kayyade musamman ilimin harsuna na da zumunci database , da kuma yi amfani da zama dole bayani. Kamar wancan ne daban-daban saka suna database abubuwa goyon kai tsaye a kan harshen matakin a ji cewa cikin hira ne da za'ayi da mai tarawa abu sunayen a ciki identifiers, dangane da goyon sabis alluna musamman-kundayen. A core na kula da tsarin, bisa manufa, ba hulɗa tare da alluna ko mutum ginshikan.

A SQL harshe ya hada da wani jerin musamman kayan aikin domin ayyana database saka. Sa'an nan, wani irin hani suke kunshe a cikin na musamman Tables, taskoki, da kuma mutunci monitoring ne da za'ayi kai tsaye a kan rabe-raben harsuna matakin, cewa shi ne, a aiwatar da karanta mutum database gyara kalamai tarawa, dangane da samuwa a cikin database mutunci constraints, ciyarwa don samar daidai code.