跟讀練習: Oracle database architecture explanation in details - 通過影片學習英語口語
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Hi friends, today in this video I am going to talk about Oracle Database.
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Oracle Database is basically one of the most demanding database which has started by Oracle Corporation in 1971.
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So even when you are starting your career as Oracle Database,
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in most of the interview you will get so many questions from Oracle Database Architect.
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So in that perspective also and even for learning Oracle Database,
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this is one of the most demanding topic that you have to must learn with deep understanding.
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So I am going to explain with my personal experience on Oracle Database because I am a database administrator.
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So with my personal understanding,
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with my personal experience, I am going to explain the whole architecture.
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so yeah first of all whenever any end user wants to connect
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or a database so it connects through use any client machine
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or through any application end user application
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or even through sql developer there are multiple platform from there you people connects to the database
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so you know client machine it will create a user user process
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and between user process
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and server process there will be a listener listener will have information about the host
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and port of an database with on the
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with that it will decide which database it has to connect so it will it will generate a one dispatch
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dispatcher request when that dispatcher will send that request to the server process
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and server process are when
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when you create a database by default it creates a dedicated server process
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and server process basically sits on uh servers oracle server side
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so when we create a database it will get created by default it will be a dedicated server process
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and for dedicated server process it will create a PGA
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that is called program global area but
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if you are choosing a shared global area for that it will create UGA that is user global area.
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So server process is basically responsible for making that connection to the database
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because it's interact to the database so it will send
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that request to the database like if we are firing any uh selected statement
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or any sql on a database so from server process it will go to a
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sga sga is a shared global area basically is the is it's the largest part of the database instance
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and the database is basically combination of instance background process
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and the physical files so physical files are basically data file redlock file
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and control file so these are the physical files and yes SGA is also the combination of different sub components
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so in that whenever
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that request will come from server process it will it will go to share pool first of all
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and in share pool there are two sub components
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that one is library cache and another is dictionary cache library cache is basically information of most recently executed SQLs
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so most recently executed SQLs are basically when
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that request goes from server process to SGA it will do the syntax check like
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if that query is selected star from employee
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so syntax it will validate from there like
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if you execute select from employee it will not execute because the syntax is missed here like star is missed.
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So it will not it will throw the error.
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So that part is happening from library cache because it will do the syntax check,
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cement text check and privilege checks are happening on share pool itself.
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So, when the syntax check will happen after that it will validate
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if it will find
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that yes this SQL is present on the buffer cache then it will fetch
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that particular query output
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and it will return to the server process it will return to the client machine
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and that that's the same process is getting followed for in case
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if that particular SQL is not present in library case then it will create a execution plan for that and also like
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yes data dictionary case is a metadata of a database like
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it will have a object information like table views are stored into this
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so it will it will do the validation from data dictionary case as well as
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when library case will will not find that particular SQL it will
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generate a new execution plan that is basically goes for hard parishing and there is two words
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that we use in a database when any SQL get executed on a database side,
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it will go to soft parishing either it will go to hard parishing.
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So, soft parishing is the first case where it will find the SQL from the library cache itself
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and then it will fetch the data from memory buffer cache memory and it will return to the client.
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But in hard parishing case,
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will create a new execution plan and it will go for optim or through a optimization in that it will
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it will it will check from the buffer case if
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that not there then after creating execution plan it will then the background process will come into the picture
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and db writer will fetch that
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DB writer will fetch
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that particular data as per the query request it will fetch the data from the data file
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and it will return to the library cache and library cache will
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buffer cache sorry buffer cache and then DB buffer cache will return that
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to server process and server process will return to the client so that's how
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it works
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so the next is as we know buffer cache is doing
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all the things whatever the queries are coming it is getting executed in buffer cache itself
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and it stores the in case
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if you are executing any like a database change statement queries like insert or create or something like any DML.
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So in those situation it will do the changes on the data
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and in that situation read log and online read log and buffer
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read log buffer will come into the picture so there first of all buffer case will change that
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after doing the modification on the query it will get converted into a dirty buffer
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and that dirty buffer will get written to the online reader log it might be uncommitted transaction
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or it may it may be a committed transaction
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so both can be possible
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and from a read a log buffer it will get written
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to the read a log file through log writer log writer
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is responsible it's also a background process these are basically a
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mandatory background process background processes are basically two type back mandatory background process and optional background process so
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library cache is a mandatory background process
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which is responsible for copying online redlock buffers to the online redlock files
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so here redlock files are basically two online redlocks we can create like as per need we create
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that redlock files so first it will start writing to read log one after
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that once it will get filled up it will done the online read log switch will happen
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and then it will start writing to second online read log so that's how whatever the change
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transaction change modified data will come from online read log buffer to the
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read log it will get written to log 1 and log 2
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and similarly till the time after
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that it will get written to through archiver process there is a optional optional background process
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that is called archiver with with the help of
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that it will get written to the archive read log
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that we'll use for our backup
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and recovery of our database in case i am our database fails
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or it get crashed for any reason so that will be used for recovery so yeah so the next is
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assist if we focus of our mandatory background process
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so as one is system monitors as money is basically used for instance recovery
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and yeah even for temporary table space management also it
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will be responsible PMON is responsible for our transaction transition rollback
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and for PMON is process monitor which is responsible for user session recovery
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and doing the cleanup or even rollback statements this is responsible for making those cleanups on database
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and yeah check pointer is a background process which is updating the scn number to data file and on
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control control control file control file is a brain of a database
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which will which will have information about the database creation and all the data file information and detail about the database.
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So, this control file will be considered as a brain of a database.
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So, SCN number whenever SCN number is getting generated very frequently through whenever the check pointer occurs,
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the time SCN number is getting generated and
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that is getting updated to the header of a data file
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and control red log control file so yes there are some condition
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when the log writer writes log writer writes whenever the online red log is more than 1 GB
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or its one third full
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or even every 3 second log writer writes the data on the buffer read log buffers to the online read log files.
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So similarly there are few condition on
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that basis DB writer writes those online read logs to the
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online buffer cases changes to the data file like whenever the buffer case dirty buffer is filled up
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or even its its there is no space left in the buffer cache
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or even whenever any trunk truncate or any drop statement table space drop
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or truncate statements are getting executed or even for every commit basically the DB writer writes and log writer
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before the DB writer so that is also one condition
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when log writer writes so these are the condition
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when the log writer writes so apart from there is a parameter file
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and password file parameter file is basically a file
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which will it's a file which stores the information of every component which is
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showing on the figure as a shared pool sga sga max sga target
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and buffer cache a red log java pool large pool this
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uh parameters uh this this components are uh declared into a
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parameter file with how much size we we need it so those things are declared all the instance related come
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parameters are declared into parameter file
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so parameter files is two type like one is P file
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and the another is SP file P file we we called it any dot aura file
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and the this file is basically a static file
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and SP file is a dynamic file so
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if we are doing any change in p file for
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that we have to restart our database
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and basically for for starting our instance p file is responsible to to allocate the sga
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so p file is equally important without p file we our database cannot run
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and the next is password file it is used for user authentication
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so this is the whole thing about the database in
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that data file is actual physical file
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and read lock files are all the change transactions are getting stored into
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that and control file already I explained it
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so this is the whole thing about the database
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and this all components are like very much important yeah Java
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pool basically this Java pool are getting used at the time
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when you execute a statement with jvm or java related uh statements for
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that case java pool is getting used
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and large pool is getting used at the time
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when uh we are performing any uh arman backup with i um higher higher io
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and for our recovery um yeah for database recovery
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in those conditions large pool is getting utilized
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so this is the whole database instance that i have explained
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if you any doubt please comment below thanks for watching till here
FOR YOU
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背景與上下文
在這段影片中,講述者分享了關於Oracle資料庫的詳盡架構解釋。他強調了學習Oracle資料庫的重要性,尤其是在求職面試中,許多問題都圍繞資料庫架構展開。作為一名資料庫管理員,他從個人經驗出發,詳細闡述瞭如何通過客戶端與資料庫連線,以及各個程序之間的相互作用。這為希望深入理解和掌握資料庫知識的學習者提供了寶貴的資訊。
日常交流的五個重要短語
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- 選擇合適的句子:從影片中選擇有代表性的句子進行跟讀,確保理解句子的結構和語法。
- 逐句聽讀:多次播放每個句子,嘗試模仿講述者的發音和語調,提升語感。
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說話人最常用的結構,並附上影片中的原話:
| 結構 | 影片中的用法 |
|---|---|
| 被動語態 be + 過去分詞 — 強調發生了什麼,而不是誰做的 | is called · is selected · is missed |
| 定語從句 who / which + 從句 — 補充說明人或事物 | database which has · monitor which is · process which is |
| 現在完成時 have/has + 過去分詞 — 過去發生但與現在仍有關聯的事 | has started · have explained |
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