SCPT 1: What is Oracle Database Server
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SCPT 1: What is Oracle Database Server


Wel come back to your oracle dba tutorial In this tutorial we are going to discus about What is a 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 ok 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 taklking 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 ok 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 ok 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 Sililarly 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 ok 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 ok 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 ok So on as long as i am runing out of memory
or runing out of hard drive where this file are stored ok 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

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