Database vs Instance
Oracle yog RDBMS (cov khoom lag luam ntsig txog kev tswj hwm qhov system) uas siv dav hauv kev lag luam. Nws yog tsim los ntawm Oracle Corporation. Ib qho Oracle system yog tsim los ntawm tsawg kawg ib qho piv txwv thiab cov ntaub ntawv. Piv txwv li yog ib phau ntawm cov txheej txheem uas sib txuas lus nrog cov ntaub ntawv khaws cia. Database yog qhov chaw cia, uas tuav cov ntaub ntawv sau. Txawm li cas los xij, lo lus Oracle database yog siv los xa mus rau tag nrho Oracle database system (xws li thiab databases). Vim li no, muaj ib txwm tsis meej pem rau cov pib ntawm cov ntsiab lus database thiab piv txwv.
Qhov piv txwv yog dab tsi?
Instance yog ib qho kev sau ntawm cov txheej txheem ua haujlwm saum toj kawg nkaus ntawm lub operating system thiab cov cim xeeb cuam tshuam uas cuam tshuam nrog cov ntaub ntawv khaws cia. Qhov piv txwv yog qhov sib cuam tshuam ntawm tus neeg siv thiab cov ntaub ntawv. Cov txheej txheem muaj peev xwm sib txuas lus nrog tus neeg siv khoom thiab nkag mus rau cov ntaub ntawv yog muab los ntawm qhov piv txwv. Cov txheej txheem no yog cov txheej txheem keeb kwm yav dhau los thiab lawv tsis txaus los tuav ACID (Atomicity, Consistency, Isolation, and Durability) hauv paus ntsiab lus. Yog li, ib qho piv txwv kuj siv ob peb lwm yam xws li nco cache thiab buffers. Tshwj xeeb tshaj yog, ib qho piv txwv yog tsim los ntawm peb ntu. Lawv yog SGA (System Ntiaj Teb Cheeb Tsam), PGA (Program Global Area) thiab cov txheej txheem keeb kwm yav dhau. SGA yog lub cim xeeb sib koom ib ntus, uas muaj lub neej ntev ntawm qhov piv txwv pib rau nws kaw.
Database
Oracle database hais txog qhov tseeb cia ntawm Oracle RDBMS. Nws yog tsim los ntawm peb lub ntsiab. Lawv yog cov tswj cov ntaub ntawv, redo cov ntaub ntawv thiab cov ntaub ntawv cov ntaub ntawv. Optionally yuav muaj cov ntaub ntawv lo lus zais hauv cov ntaub ntawv. Cov ntaub ntawv tswj xyuas kom taug qab txhua cov ntaub ntawv cov ntaub ntawv thiab rov ua cov ntaub ntawv. Nws kuj tseem pab khaws cov ntaub ntawv kev ncaj ncees los ntawm kev ua raws li System Change Number (SCN), timestamps thiab lwm yam ntaub ntawv tseem ceeb xws li cov ntaub ntawv thaub qab / rov qab. Cov ntaub ntawv khaws cov ntaub ntawv tiag tiag. Thaum lub sijhawm tsim database, tsawg kawg yog ob cov ntaub ntawv cov ntaub ntawv raug tsim. Cov ntaub ntawv no pom lub cev los ntawm DBA (Database Administrator). Cov ntaub ntawv ua haujlwm xws li renaming, resizing, ntxiv, txav lossis xa rov tuaj yeem nqa tawm ntawm cov ntaub ntawv cov ntaub ntawv. Redo log cov ntaub ntawv (tseem hu ua online redo cav), khaws cov ntaub ntawv hais txog kev hloov pauv ntawm cov ntaub ntawv nrog cov ntaub ntawv tshawb fawb. Cov ntaub ntawv no yog xav tau yog tias tus neeg siv yuav tsum rov ua dua tag nrho lossis qee qhov kev hloov kho ntawm cov ntaub ntawv. Txhawm rau ua piv txwv los tswj cov ntaub ntawv ntawm cov ntaub ntawv, nws yuav tsum qhib nws ua ntej. Ib qho piv txwv tuaj yeem qhib tsuas yog ib qho database. Txawm li cas los xij, lub database tuaj yeem qhib los ntawm ntau qhov xwm txheej.
Dab tsi txawv ntawm Database thiab Instance?
Cov ntsiab lus piv txwv thiab cov ntaub ntawv hauv Oracle RDBMS muaj feem cuam tshuam, tab sis lawv xa mus rau ob qhov sib txawv hauv qhov system. Cov ntaub ntawv hais txog qhov tseeb khaws cia ntawm RDBMS, thaum Instance yog ib qho kev sau ntawm cov txheej txheem khiav saum toj ntawm lub operating system thiab cov cim xeeb muaj feem cuam tshuam nrog cov ntaub ntawv khaws cia. Piv txwv li yuav tsum qhib lub database ua ntej manipulating cov ntaub ntawv. Ntau qhov xwm txheej tuaj yeem qhib ib qho database, tab sis ib qho piv txwv tsis tuaj yeem qhib ntau lub databases.
