Video: Ob theem xauv nrog piv txwv yog dab tsi?
2024 Tus sau: Lynn Donovan | [email protected]. Kawg hloov kho: 2023-12-15 23:47
Hauv databases thiab kev ua lag luam, ob - theem xauv (2PL) yog ib qho kev tswj hwm kev sib koom ua ke uas tau lees paub serializability. Nws kuj yog lub npe ntawm qhov tshwm sim ntawm cov txheej txheem kev lag luam database (keeb kwm).
Muaj zog nruj ob - theem xauv.
| Xauv hom | nyeem- xauv | sau- xauv |
|---|---|---|
| sau- xauv | X | X |
Tsis tas li ntawd, ob theem ntsuas phoo yog dab tsi thiab nws lav serializability li cas?
Ob - theem xauv : Ob - theem xauv schema yog ib qho ntawm cov xauv schema yog qhov kev hloov pauv tsis tuaj yeem thov qhov tshiab xauv kom txog thaum nws qhib cov haujlwm hauv kev sib pauv. Nws koom nrog ob theem.
Kuj Paub, cov txiaj ntsig dab tsi ua rau kev kaw ob theem nruj? Teb: nruj ob - theem xauv muaj cov qhov zoo ntawm nruj 2PL . Nyob rau hauv tas li ntawd, nws muaj cov cuab yeej uas rau ob tsis sib haum xeeb muas, lawv cog lus kev txiav txim yog lawv qhov kev txiav txim serializability. Hauv qee lub tshuab cov neeg siv yuav xav tias tus cwj pwm no.
Dab tsi yog nruj ob theem xauv?
nruj ob - theem xauv : Kev hloov pauv tsis tuaj yeem sau rau hauv cov ntaub ntawv kom txog thaum nws tau mus txog nws qhov kev cog lus. Kev hloov pauv tsis tuaj yeem tso tawm ib qho xauv kom txog thaum nws tau sau tiav rau hauv cov ntaub ntawv; yog li ntawd xauv tsis tso tawm kom txog thaum tom qab qhov kev cog lus.
Yuav ua li cas yog ob theem xauv raws tu qauv kom serializability?
Vim tias qhov tsis sib xws tsuas yog tsim los ntawm kev sau ntawv. Ntau qhov kev nyeem ntawm cov khoom siv database tuaj yeem tshwm sim ua ke. 2- Phase Locking raws tu qauv txwv qhov tsis xav tau nyeem / sau los ntawm kev thov tshwj xeeb xauv . Ntxiv mus, thaum muaj kev tshwj xeeb xauv ntawm ib yam khoom nws tsuas yog tso tawm hauv shrinking theem.
Pom zoo:
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