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My readings

All posts relating to Oracle database administration.

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anilvvkumar
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Re: My readings

Postby anilvvkumar » Tue Sep 17, 2013 3:49 pm

Sir,

I have downloaded Oracle database concepts pdf from net. I have started to read the contents. Thanks for your information.

Thanks & Regards,

Anil Kumar

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Re: My readings

Postby Tim... » Tue Sep 17, 2013 7:42 pm

You won't regret it!

Cheers

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anilvvkumar
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Re: My readings

Postby anilvvkumar » Wed Sep 18, 2013 11:00 am

Sir,

I didn't understand related to regret. It means, I am not regret becuase of my failure interview?

Thanks

Anil Kumar.

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Re: My readings

Postby Tim... » Wed Sep 18, 2013 1:43 pm

No. :)

I meant you will not regret reading the Concepts Manual. :)

Cheers

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anilvvkumar
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Re: My readings

Postby anilvvkumar » Wed Sep 18, 2013 5:48 pm

OK Sir.

I will read it throughly. And I ask the you if any doubts.

Getting the master like you is very difficult. I feel I am happy becuase of you. As you are giving good support.

By the by, I would like to know what is your working timings I mean, what is your frequency of replying messages

You are giving reply in this focum by sitting in office or house, could you tell me your working details with frequency of repling messages in Indian Standard Time.

I am working from 3.00 PM to 12 AM, it is in evening shift.


Anil Kumar.

anilvvkumar
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Re: My readings

Postby anilvvkumar » Wed Sep 18, 2013 7:17 pm

Sir,

I read in Database concepts manual as "Each client process is associated with its own server process. The server process has its own private session memory, known as the program global area (PGA)." And server is having lot of processes such as DBWn, CKPT, LGWR, ARCn, RVWR, PMON, SMON, RECO, MMON, MMNL, OTHERS.

I have a doubt all these processes use again use PGA independently. I mean PMON process use its own seperate PGA, and SMON use its own seperate PGA like wise. I got this doubt becuase I had seen a picture in internet somewhere, that each process use its own PGA to connect with SGA ?

anilvvkumar
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Re: My readings

Postby anilvvkumar » Wed Sep 18, 2013 7:20 pm

Sir,

If I want to attach something here, how can I attach ?

Thanks & Regards,

Anil Kumar.

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Re: My readings

Postby Tim... » Wed Sep 18, 2013 7:30 pm

Hi.

Regarding sessions:

For a start, when you are reading about connections, you are really talking about normal user connections, rather than background processes, so I would think of them as completely separate things.

Each session/connection has it's own PGA. That's were it holds session-specific details, like package variables, cursors and depending on the processing, full table scans my be read directly in to the PGA and bypass the buffer cache entirely.

The session does not connect to the SGA via the PGA. They are completely different memory areas. The server process associated with the session does some operations using the PGA, but for others it uses the contents of the SGA. One is not a link to the other.

Regarding my online time:

This website is not. I log on whenever I have change and try to answer questions. The frequency depends entirely on what is going on in my life and where in the world I am. Next week I will be at OOW2013, so I will be in West Coast USA time and I will probably not be answering many questions as I will be at the conference. Like I said, it's not my job, so I do what I can, when I can.

Regarding Uploads:

No you can't upload anything. This forum should just be for simple questions. Uploading documents and stuff like that is not appropriate. If it can;t be put into a couple of paragraphs or a simple SQL test case, you probably shouldn't be asking it here and I probably don't have the time to answer it. :)

Cheers

Tim...
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anilvvkumar
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Re: My readings

Postby anilvvkumar » Thu Sep 19, 2013 12:08 pm

Sir,

Thanks for reply.

It is clear from documents related to client processes and server process. I mean client process connects to server process, and the server process connects to SGA through PGA. That is also in picture. Is it ok?

And server process means DBWn, CKPT, LGWR, ARCn, RVWR, PMON, SMON, RECO, MMON, MMNL and others. I came to know that others are different with server processes.

Related to sessions, a session is having client process, server process. A process will be used by a session to execute statements. SESSION will grab a process from a pool of processes in
order to execute a statement. When the call is over, that process is released back to
the pool of processes.

Thanks & Regards,

Anil Kumar.

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Re: My readings

Postby Tim... » Thu Sep 19, 2013 1:03 pm

Hi.

1) No. A server process uses both PGA and SGA. It does not connect to the SGA through the PGA. Can you give me a URL to that diagram so I can see if I can understand your misunderstanding.

3) The problem here is you seem to be mixing together the concepts of dedicated server and shared server. In dedicated connections, each session has its own server processes. In shared server, multiple sessions share the same server processes with traffic directed through a dispatcher. These are two very different ways of session management and should not be confused.

See: http://docs.oracle.com/cd/E11882_01/ser ... m#i1006130

Also, be careful what you mean by client process. From a database perspective the session just has a server process. The "client" process the docs discusses is not an Oracle process. It is a client program, like a Java or .NET app. As a result, a new connection to the database does not spawn two new processes. Only one. From your description it is not clear you have understood that point. The link I sent should make that clear.

Cheers

Tim...
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anilvvkumar
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Re: My readings

Postby anilvvkumar » Thu Sep 19, 2013 1:43 pm

The URL is

http://docs.oracle.com/cd/E11882_01/ser ... htm#i62345

and also in

http://www.oracle.com/webapps/dialogue/ ... 600&Act=54

Please check in both diagrams.. server process is connected to sga through pga..

Thanks

Anil Kumar

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Re: My readings

Postby Tim... » Thu Sep 19, 2013 1:50 pm

Hi.

The client process is pointing to the server process. The server process then point to the buffer cache in the SGA. The server process has an overlap with the PGA, showing that it own/uses the PGA. There is no line from the PGA to the buffer cache. Look where the line originates. It is the server process box.

This diagram does not support your suggestion.

I've asked one of my colleagues, who is not a DBA, and he actually interpreted the diagram in the same way as you, so I guess it is not the clearest diagram possible in this sense. The diagram is correct, but the labelling of the PGA is such that it could be misinterpreted.

Cheers

Tim...
Tim...
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anilvvkumar
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Re: My readings

Postby anilvvkumar » Thu Sep 19, 2013 1:59 pm

Related to sessions kindly check this url Figure 15.2

http://docs.oracle.com/cd/E11882_01/ser ... htm#i16977

anilvvkumar
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Re: My readings

Postby anilvvkumar » Thu Sep 19, 2013 2:07 pm

Sir,

Had you checked my second diagram which is more clear and latest design of oracle. If you want I can send it to your email with attachment of that diagram. It is clear that User process is connected to server process and server process uses its own PGA, and PGA connected to SGA.

But by this discussion I can understand a server process may or may not used PGA and can directly connect to database buffer cache. Is it ok?

Anil Kumar.

anilvvkumar
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Posts: 41
Joined: Thu Aug 29, 2013 9:16 pm

Re: My readings

Postby anilvvkumar » Thu Sep 19, 2013 2:13 pm

Sir

I refered once again in both diagrams. I came to know that there is no line between between PGA to SGA, rather there is a line between server process to buffer.

But

In the second diagram there is a clear line from PGA to buffer cache.

Kindly please check it once. It is the latest diagram of Oracle. Its not in their documents. It is in database interactive quick reference. For the sake of mine please refer that document. Then you will also come to know.

Regards

Anil Kumar.


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