03 -SGBD - Oracle 1
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Transcript of 03 -SGBD - Oracle 1
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Introducere
Slide 1
Slide 2
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Slide 3
Slide 4
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Baza de date si instanta
Slide 5 – BD structura de fisiere
Slide 6 – BD structura de fisiere
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Slide 7 – BD Tipuri de fisiere
Slide 8 – BD Tipuri de fisiere
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Slide 9 – BD Tipuri de fisiere
Slide 10 – Structura fizica a BD
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Slide 11 – Structura logica a BD
Serverul Oracle foloseste structuri de memorie si procese distincte pentru accesarea bazei de date. Structurile de memorie se afla în memoria principala a sistemelor ce constituie sistemul de baza de date. Procesele sunt functii (sarcini) ce opereaza în memoria acestor computere.
Instanta Oracle
Instanta Oracle contine structurile de memorie interna si procesele care asigura functionalitatea clasica a unui SGBD.
La nivelul sistemului de operare aceasta este un serviciu distinct identificat printr‐un anume SID (numele personalizat al instantei)
Când un utilizator cere o conexiune la baza de date printr‐un proces utilizator (ex. SQL Plus), cererea este preluata în prima faza de un serviciu numit listener, a carui sarcina este sa interpreteze string‐ul de conectare (numele bazei de date furnizat de catre utilizator) si sa verifice daca exista un serviciu instanta corespunzator. Daca instanta indicata exista si este activa , se creeaza câte un proces server pentru fiecare conexiune care va rezolva cererile exprimate prin comenzile SQL ale utilizatorului.
Instanta Oracle este elementul esential care asigura functionalitatea specifica SGBD‐ului, si se materializeaza sub forma unui serviciu specific. Concret, aceasta este formata dintr‐o zona de memorie interna, numita System Global Area, si o serie de procese background care functioneaza într‐o maniera colaborativa.
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Slide 12 – O singura instanta
Slide 13 – Instante multiple
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Real Application Cluster
Sisteme cu instante multiple
Exista arhitecturi hardware care permit ca mai multe computere (procesoare) sa partajeze accesul la date, software sau dispozitive periferice. Aceste arhitecturi ruleaza instante multiple ce partajeaza o singura baza de date fizica.
Slide 14
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Structuri logice de stocare
Slide 15 – Sistemul de fisiere
Slide 16 – Sistemul de fisiere vs Spatiile Tabela (Tablespaces)
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Slide 17 – Spatiile Tabela (Tablespaces)
Slide 18 – Segmente
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Slide 19 – Segmente
Slide 20 – Blocuri
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Slide 21 – Structuri logice de stocare
Spatiile tabela (tablespaces)
Slide 22 – Tablespaces
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Slide 23 – Tablespaces
Slide 24 – Tablespaces
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Slide 25 – Vizualizarea tablespaces din contul SYS (DBA pentru BD)
Slide 26 – Vizualizarea tablespaces din contul STUDENT (user obisnuit pentru BD)
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Slide 27 – Vizualizarea tablespaces din contul SYSTEM (DBA pentru BD)
Slide 28 – Tipuri de “Tablespaces”
Bigfile tablespace: A Bigfile Tablespace is a special kind of tablespace than can only have a single (normally very large) datafile. Bigfile tablespaces can be up to 4G blocks that 128 TB with 32k blocks. Normal tablespaces are referred to as smallfile tablespaces.
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(Sursa: http://www.orafaq.com/wiki/Bigfile_tablespace)
Slide 29 – Tipuri de “Tablespaces” (Temp Tablespace)
Slide 30 – Tipuri de “Tablespaces” (System Tablespace)
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Segmente si extensii de date
Slide 31 – Extensia
Slide 31 – Segmentul
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Segmentul este cea mai mica unitate de stocare cu care interactioneaza direct utilizatorul
Cand se creeaza un obiect in BD se creaza un segment nou, asociat obiectului (tabela, index, etc)
Initial unui segment ii sunt atribuite un anumit numar de extensii a caror marime (numar de blocuri contigue) poate fi stabilita exact.
Slide 32 – Extinderea unui segment
Numarul extensiilor care se adauga precum si dimensiunea acestora poate fi controlata de catre utilizator.
Slide 33 – Extinderea unui segment
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Blocuri de date
Slide 34 – Octetul (Byte)
Slide 35 – Octetul (Byte)
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Slide 36 – Blocul de date la nivelul sistemului de fisiere
Blocul este alcatuit dintr‐un nr. fix de octeti (functie de sistemul de operare; de sistemul de fisiere)
Ex: SO Linux ‐ system de fisiere ext3 admite:
SO –Windows
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Slide 37 – Blocul de date la nivelul Bazei de date (BD)
Exemplu: OS Block 512 bytes; Data Base Block Size 1024 sau 2048 bytes
Cand se “citesc” date de pe hard disk daca se citesc date din BD Oracle in memorie este adus cel putin un bloc de date al bazei de date. Pentru orice alta citire de pe hard disk in memorie se aduce cel putin un bloc de date specific sistemului de fisiere (SO).
Marimea blocului de date este dictata de un parametru al fisierului de initializare a BD Oracle (DB_BLOCK_SIZE).
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Tipuri de segmente in BD
Structura logica de stocare
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Structura logica a BD