What is Oracle Database Server
So lets consider a example of a human so a human being consists of so lets its a human so this human name is scott Scott have two hand and paie of legs pair of eyes and so on all right
And then also scott has on a memory where he remember something where he things something right Then lets say the scott is a ginious person and he can able to write in ver fast day when he came to this world So this is a someson that this scott is a ginious and scott could write in the very fast second he come to this world What happend their parents give scott some notebook to write ok so then what scott did Scott started to write about that what is hapening in an around him or what is hapening to him in a note book like this
And ones this note book is completed he goes to another notebook and so on All right so lets say the scott this is about whats about scott story so what esentialy scott has scott has a memory small memory where he remember something but what he does
Because he forget he is to write those thing from his memory to the note book ok so this what about scott Then i going to draw a line here so in this part i am talking about human and in this part talking about his diary notebooks where he is going to write things about him This analogy is exactly same if we consider oracle database server
What essentialy oracle database server is is consist of instance and instance is basicaly something memory plus some background proceses or just some proceses.So like the way of scott has a hand we have some background proceses
So scott write using his hand and we have a background proceses called db writer so What db writer does it writes to database file ok so we have instance and some file
So this is what is essentialy oracle database server and why we started at human becouse this is analogus.
So Scott is equivalant to instance and this memory equivalant to this memory this guy has then the eay that is guy has a hand eyes hands and ears, we have something called background processes
The way this guy have some notebooks where he write we have files ok and all these things together called oracle database server
So lets do a formal picture so formal picture something like this A oracle database server is consists of procesec p1 p2 p3 and plenty of them We are discus all these things in leter videoes like what each proceses does and what is each proceses responsible fast and then we have a memory structure.
All right then the equivalent of notebook to show in our human one example we have something called database file
So this is called instance and this is called database and the whole thing the complete thing called oracle db server
This is lot of people ask the instance and databse are same this is compeletly wrong instance is the human where database is the file.
You can think about just way so if my picture like good this is a abstract picture of db server this is called db files and this called top part instace they worked together that
means instance will attached this files then they worked in vry sufisticated way
In a very corrdinate way so that we can how the database going to work so we are discusing.
in later videoes we have series of videoes frm now where we discus in very detail about all these procesec memory structure database files and all these things
So here is anothers question the people are ask gow many database server can be run in a meachine ok
S the answer is depends so how big is your meachine is so lets say what i am saying that i have a meachine right so in this meachine i fast install a oracle db server
In that time i create instance one and database file one so this is a oracl db server essentialy if u do not tune anything by default may be this instant oracle 11g server is going take around five seven hundred fifty run
So if you instal one of these oracle server it is going to contain 750 mb ram of this meachine Lets say asume this meachine has 2 gbt of memory then can also have another instance i2 with data file 2
So on as long as i am runing out of memory or runing out of hard drive where this file are stored.
Therefor their is not definitely one you can have multiple db server depend on how much memory how much hard drive you have
Another thing that u say we have instace then we have files instance attached with file and they worked in a cordinated way
This is 1 2 1 maping where each instance is a associated one db file to one database that is called single instance server
If that is so we also have datafile we can have multiple instances i1 and i2 they can be attached to the same database file In this case this system is called oracle paralel server or they have a fency name which is called rac real application cluster
So you can ask another question how many instances can have it depends like i have seen their 64 node racks
That we have 64 instances they are working with attached to a single db file system However you might have another question that can i have a db file system or 2 db file system
that can be attached to one instance the revourse of this thing one instance we have multiple db file system
No that is not possible because in database we have lotoff properties like atomocity consistency and all these things
And we can not do if you want to use multiple database files and we have only one instance 2 or quit ok
So theirfor this senario not exit we have 1 2 1 or we can have multiple instances with one database file
So this is all about what is oracle database server again i am going to summerige oracle database server consists of 2 things one is called instace and second one is called database files or this is called database
And whole complete thing is called oracle database server and again instance is two thing like proceses and memory structure and if i do a human analogy this is like legs
hands and so on This is like a small memory like ram and imagine this memory is small compare what i store
in my notebooks if i completed one notebook i buy another one and continue drive that But if i finish my memory in brain i can not add memory ok
So that means what i am saying this partis very costly where as you just keep ading the disk and so on
So this is what exactly what we are seeing as human being and i am just giving an analogy that what is an oracle database server
So hope u understand this we are going to follow more videos database structure please make sure that u follow dba series on the according to the order