ACID imateteza Data wa Database
Mmene ACID imagwirira ntchito yosungirako ma deta ndi imodzi mwa mfundo zakale kwambiri komanso zofunikira kwambiri za chiwerengero cha deta. Zimakhazikitsa patsogolo zolinga zinayi zomwe machitidwe onse oyendetsera masanjidwe amayenera kuyesetsa kukwaniritsa: atomu, kusasinthasintha, kudzipatula ndi kukhazikika. Deta yachinsinsi yomwe imalephera kukwaniritsa zolinga zinayi izi sizingaganizidwe kukhala zodalirika. Deta yapamwamba yomwe ili ndi zizindikiro izi imalingaliridwa ngati ACID.
Idafotokozedwa ndi ACID
Tiyeni titenge kamphindi kuti tifufuze chimodzi mwa zizindikiro izi mwatsatanetsatane:
- Atomicity imanena kuti kusinthidwa kwa deta kumatsata malamulo onse "kapena ayi". Kulipira kulikonse kumatchedwa "atomiki." Ngati gawo limodzi la malonda likulephera, ntchito yonseyo imalephera. Ndikofunika kuti dongosolo la kayendedwe ka mabungwe apakompyuta ligwiritse ntchito atomiki yamagetsi ngakhale kuti pali DBMS iliyonse, ntchito yolephera kapena hardware kulephera.
- Chigwirizano chimanena kuti deta yeniyeni yokha ingalembedwe ku deta. Ngati, pazifukwa zina, malonda akuchitidwa omwe amatsutsana ndi malamulo a mgwirizanowu, ntchito yonseyo idzabwezeretsedwanso, ndipo detayi idzabwezeretsedwa ku boma mogwirizana ndi malamulowo. Kumbali ina, ngati ntchitoyo ikugwirizanitsa bwino, idzatenga deta kuchokera ku dziko limodzi lomwe likugwirizana ndi malamulo ku dziko lina lomwe likugwirizananso ndi malamulo.
- Kusungulumwa kumafuna kuti kuchulukana kwambiri kubwerere panthawi yomweyi sikuphatikizana. Mwachitsanzo, ngati Joe akugulitsa ntchito yosungirako deta panthawi imodzimodziyo kuti Mary akupereka zosiyana, zonsezi ziyenera kugwiritsidwa ntchito pazomwezi. Mndandanda wazomwezi uyenera kuchita Joe ntchito yonse asanachite Mary's, kapena vice-versa. Izi zimalepheretsa kugulitsa kwa Joe powerenga deta yapakati yomwe imapangidwa ngati mbali imodzi ya gawo la Mary zomwe sizidzatsimikiziridwa ku database. Dziwani kuti malo osungulumwa sakuwatsimikizira kuti ntchito yoyamba idzachita chiyani - kungoti kusagulitsa sikungasokoneze wina ndi mnzake
- Kukhazikika kumatsimikiziranso kuti malonda onse opangidwa ku database sakutha. Kukhazikika kumatsimikiziridwa pogwiritsira ntchito zida zogulitsira malonda ndi zolemba zomwe zimapangitsa kuti kubwezeretsedwa kwa zochitika zogwiritsidwa ntchito zithetsedwe mosasamala kanthu za zovuta zina zamapulogalamu kapena zoperewera zakuthupi.
Mmene ACID imagwirira ntchito
Otsogolera deta amagwiritsa ntchito njira zingapo kuti akwaniritse ACID.
Chimodzi chomwe chimagwiritsidwa ntchito kukakamiza atomu ndi kupirira ndi kulemba-kutsogolo kusaka (WAL) kumene tsatanetsatane iliyonse yalembedwera ku logi yomwe imaphatikizapo kubwezeretsa ndi kufotokozera zambiri.Zomwezo zimatsimikizira kuti, chifukwa cha kulephera kwachinsinsi kwa mtundu uliwonse, database lolemba ndikuyerekezera zomwe zili mkati mwa deta.
Njira ina yogwiritsira ntchito atomu ndi kukhalitsa ndi mthunzi-kutsegula kumene tsamba lamthunzi likulengedwa pamene deta iyenera kusinthidwa. Zosintha za funsoli zalembedwera ku tsamba lamthunzi mmalo mwazomwe zilipo m'masitomala. Mndandanda wachinsinsi umasinthidwa pokhapokha ngati kukonzanso kwatha.
Njira ina imatchedwa gawo la magawo awiri omwe amapanga ma protocol, makamaka othandizira mu machitidwe omwe amasungidwa. Pulogalamuyi ikulekanitsa pempho kuti lisinthe deta mu magawo awiri: gawo lopempha pempho ndikupereka gawo. Mu gawo lopempha, ma DBMS onse pa intaneti zomwe zimakhudzidwa ndi malondawo ayenera kutsimikizira kuti alandira ndipo ali ndi mphamvu zogulira. Kamodzi katsimikiziridwa kamalandiridwa kuchokera ku ma DBMS onse oyenera, chigawochi chimatsiriza momwe deta ikusinthidwa.