Kev cais ntawm kev tswj ntawm cov tswj kev ua li cas thiab thaum twg cov kev hloov tau ua nyob rau hauv ib lub database
Kev rho tawm yog ib qho tseem ceeb ntawm txoj kev ua lag luam ntawm cov lag luam. Nws yog peb yam khoom ntawm ACID (Atomicity, Consistency, Isolation, Durability) thiab cov khoom no ua kom paub meej tias cov ntaub ntawv muaj tseeb thiab meej.
Kev rho tawm yog lub hauv paus-theem khoom ntiag tug uas tswj xyuas tau li cas thiab thaum twg cov kev hloov tau thiab yog tias lawv pom ib leeg. Ib qho ntawm cov hom phiaj ntawm kev rho tawm yog cia ntau yam kev nqis tes ua rau tib lub sij hawm uas tsis cuam tshuam lwm qhov kev sib tw.
Yuav Ua Li Cas Thiaj Ua Haujlwm
Piv txwv li, yog tias Joe hais txog kev lag luam tawm tsam tib lub sij hawm uas Mary hais txog kev sib txawv, ob qhov kev lag luam yuav tsum khiav lag luam nyob rau hauv cov ntaub ntawv keeb cais. Tus database yuav tsum ua kom tiav Joe's tag nrho lw ua ntej executing Mary lossis vice versa. Qhov no tiv thaiv Joe's lw los ntawm kev nyeem ntawv cov ntaub ntawv uas tau tsim ua ib feem ntawm ib feem ntawm Mary's lw ua haujlwm uas tsis yog nws yuav tsum cog lus rau lub database. Nco ntsoov tias cov cuab yeej kev sib cais tsis paub meej hais tias qhov kev ua lag luam twg yuav ua thawj zaug, tsuas yog tias lawv yuav tsis cuam tshuam nrog lwm tus.
Kev Txiav Txim Siab
Muaj plaub theem kev sib cais:
- Serializable yog theem siab, uas txhais tau hais tias cov muas yuav tsum tiav ua ntej lwm lw pib tau.
- Repeatable nyeem pub yais kom tau nkag thaum lub sijhawm pib, txawm tias nws tsis tau tiav lawm.
- Nyeem cog lus tso cai rau cov ntaub ntawv yuav tsum tau nkag mus tom qab cov ntaub ntawv tau raug cog lus rau lub database, tab sis tsis ua ntej ntawd.
- Nyeem tsis tau yog qhov qis tshaj ntawm kev cais thiab tso cai rau cov ntaub ntawv yuav tsum tau nkag ua ntej cov kev hloov tau.