All language subtitles for [SubtitleTools.com] Understanding Oracle Connections - Learning Oracle 12c [Video]

In this lesson,
we're going to talk

about how connections
are made to an Oracle

database via a network.

So that's all about how Oracle
does its networking component.

And Oracle's
networking stack that's

included with its database
product is called Oracle Net.

Now it's been called
many different things

through previous versions,
such as SQL Net, Net 8,

and so on and so
forth, but Oracle Net

is the name given
to it at this point.

And Oracle Net is
really an amazing thing

because it allows a user
to connect to a database

irrespective of the
operating systems involved.

So I can have a
client machine running

SQL Developer on Windows and
still connect to an Oracle

database running on Linux.

And there's no network
problems there because

of Oracle's networking stack.

And this has been in
place for a long time

and was really one of the
first commercial databases

to really make use
of this technology.

And truthfully, the connection
information involved and setup

are really pretty quite simple.

There's not a lot to
administer Oracle networking.

It really just
requires the knowledge

of a couple of
different subjects.

So a database can participate
in different network models.

So we can have a
client-server model,

and that's a direct connection.

So that occurs when a user,
say running SQL Developer,

makes a direct connection to
a database, client to server.

This can also be
certain applications

that make those
types of connections.

So we might build and deploy
an application to our users.

And in that application
is connection information

on how to connect directly
to an Oracle database.

So it's a direct connection,
client to server.

We also have the network model
that's really more popular

today that most DBAs would
be more likely to see,

and that's a multi-tier
network model.

And that's connection
through another server.

So that would be a situation
where a user connects

into a web server and then maybe
an application server and then

a database server.

So there's multi-tiers
involved, multiple tiers.

Oracle networking also supports
two major server architectures

for the Oracle database.

The first is called
dedicated server.

Dedicated server setup,
a connecting user

is given a dedicated server
process when they connect.

So if we have a database
and then a user,

we have a process running on
the database called a listener.

And the listener is
only there and has

only the job of listening
for incoming connections.

So Kara, when she
makes an attempt

to connect to a
database, she's actually

contacting the listener first.

If the listener
isn't running, she

won't be able to make a network
connection to the database.

Once her user name and
password are negotiated

and she is
authenticated, then she's

given her own dedicated
server process

to do work on the database.

So, on the Linux
operating system,

we would actually see that
as an individual process

out on the operating system.

And so all work that Kara does
in her session to the database

occurs through that pipe.

Oracle also supports what's
called shared server.

And this has been called a
number of different things

through past versions as well.

Multi-threaded server was
one of its previous names.

And in a shared server
model, the connecting user

is given a shared
server process.

So it looks something like this.

We have a database
here, and then we

have a process
called a dispatcher.

And the dispatcher's
job is really

to play traffic light
for incoming connections.

So between this dispatcher
and the database,

we have what's
called shared servers

or shared server processes.

So these are dedicated
connections into the database.

So we can think of them as
pipelines into the database.

But when a user tries to
connect to this database,

first, the user has to
go through a dispatcher.

And the dispatcher will decide
which shared server process

Kara gets to use.

So she may get this
shared server process.

As long as she's doing work
on that shared server process,

it acts almost as a
dedicated server process.

But the moment that
she becomes idle,

that shared server becomes
available for someone else.

So Scott, if he
were to connect in,

would get a different
shared server process.

And no matter how
many connections

are incoming to the database,
they go through the dispatcher,

and they all have to negotiate
through those shared server

processes.