Home » Other » Training & Certification » Difference Between "Redo Log Buffer" and "Database Buffer Cache"?
Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #264177] Sat, 01 September 2007 08:19 Go to next message
raksaba
Messages: 1
Registered: August 2007
Junior Member
Hi,

I am totally new to Oracle.

I just want to know what is the difference between redo log buffer and database buffer cache?

Changes to the rows/columns are stored in database buffer cache and also in redo log buffer.

then what is the necessity to have redo log buffer?

Could anyone please explain with simple example?
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #264181 is a reply to message #264177] Sat, 01 September 2007 09:01 Go to previous messageGo to next message
BlackSwan
Messages: 25050
Registered: January 2009
Location: SoCal
Senior Member
Are you unwilling or incapable of Reading Then Fine Concepts Manual
which contains answers to all your questions plus many more?

http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/toc.htm

If you won't read the answers in this manual why should folks expect you to read the answers posted here?
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #264578 is a reply to message #264177] Mon, 03 September 2007 18:37 Go to previous messageGo to next message
marcosbr
Messages: 24
Registered: April 2007
Location: Argentina
Junior Member
Hi guys

anacedent:
We don’t need to be aggressive, I’m new with Oracle and I’ve read the first chapters of the books and I’ve a lot of doubts. Of course I haven’t all the concepts perfectly clear in my first time.

raksaba:
I was reviewing the concepts a Little bit, and it seems like the Buffer cache is communicated with data files and Redo logs buffers are communicated with redo log files.

I mean: the buffer cache is communicated to a Database Writer process (DBW0) the it says to you that maybe an result of an insert command will be stored in data files (it is the common files where your data is stored) and from the other hand you have the Redo Log buffer that is communicated with the Log Writer process (LGWR) and it write into redo log files I guess because when you haven’t space in your RAM memory you need to save it in the hard disk to have all the changes saved in order to keep it ready for some restore.

I understand your question and I guess you’re thinking in the possibility to use just one buffer and maybe two processes to write in the data file one for data files and another for redo logs files. I don’t know exactly the difference between the two buffers but just think if you are an experimented programmer, always is good to separate one process that do something to another that have other objective.

I guess also that my explanation is not good enough, but is all that I know at moment and I don’t want to be more ahead of it because I’m reading chapter by chapter.

Look up this link:
http://www.exforsys.com/tutorials/oracle-10g/oracle-10g-concepts-and-database-architecture/1.html

Let me know you comments and sorry for my English.
Cheers
Marcos

[Updated on: Mon, 03 September 2007 18:40]

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Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #264641 is a reply to message #264578] Tue, 04 September 2007 01:45 Go to previous messageGo to next message
Michel Cadot
Messages: 64153
Registered: March 2007
Location: Nanterre, France, http://...
Senior Member
Account Moderator
Memory areas don't communicate, processes communicates and use memory areas.

Read Database Concepts, Chapter 8 Memory Architecture, there are a section on buffer cache and one on redo log buffer.

Regards
Michel
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266099 is a reply to message #264578] Sun, 09 September 2007 13:36 Go to previous messageGo to next message
mson77
Messages: 208
Registered: August 2007
Location: Brazil
Senior Member
Hello marcosbr,

Regarding
Quote:
anacedent:
We don’t need to be aggressive, I’m new with Oracle and I’ve read the first chapters of the books and I’ve a lot of doubts. Of course I haven’t all the concepts perfectly clear in my first time.


My opinion is that anacedent is absolutely right.

Everyone should try at least once. Should read carefully and try to understand what it is written in. Oracle documentation is the original source of information.

Regarding your comment about the differences between "redo log buffer" and "database buffer cache" and the url you have provided. The url states the right information.

Be new in oracle has one meaning and not denotes excuses.
Just my honest opinion.


mson77
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266110 is a reply to message #264177] Sun, 09 September 2007 15:54 Go to previous messageGo to next message
marcosbr
Messages: 24
Registered: April 2007
Location: Argentina
Junior Member
Of course, I’m not fighting with everybody.

But in my understood if he have asked it.., if because…he read it at least a few times, people who have this doubt if because have read the documents a few times in my opinion.

And I’ve read 2 times the Oracle.Database.10g.Administration book in the chapter 3 where I’m positioned now and I’ve similar questions, and I need some place where I can explain and share similar questions like that.

For this reason I said that.

Anyway, is obviously and I understand your point “people sometimes don’t want to read one more time or find some additional information before ask”.

In order to finish, something that we have to respect is all the opinions, wrong or not, is very important because everybody can have a mistake.

Marcos

[Edit (MC): remove portuguese sentence]

[Updated on: Sun, 09 September 2007 23:52] by Moderator

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Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266111 is a reply to message #264177] Sun, 09 September 2007 16:06 Go to previous messageGo to next message
BlackSwan
Messages: 25050
Registered: January 2009
Location: SoCal
Senior Member
http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/intro.htm#sthref94


http://download.oracle.com/docs/cd/B19306_01/server.102/b14220/memory.htm#i10221

What don't you understand about the differences in definitions?

If/when you don't understand something post URL to what causes your confusion & explain EXACTLY what you don't understand.

Do NOT ask for RTFM defintions!
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266112 is a reply to message #266111] Sun, 09 September 2007 17:29 Go to previous messageGo to next message
mson77
Messages: 208
Registered: August 2007
Location: Brazil
Senior Member
In my honest opinion... anacedent is still absolutely right.
It is my own opinion about.
Regards,


mson77
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266114 is a reply to message #264177] Sun, 09 September 2007 17:43 Go to previous messageGo to next message
marcosbr
Messages: 24
Registered: April 2007
Location: Argentina
Junior Member
Ok, anacedent how are you doing?

I’ll explain you in other words, it's my last time.

Just I’m saying you “try to be more friendly with the people”.

You want to everybody think exactly as you’re thinking and it’s no possible, 2 people don’t think equal, maybe similar but not equal . It’s proved psychologically. You can’t try to impose all that you’re thinking. Just give your Best suggestion and try to be friendly.

I want to arrive to my next certification, and I’ll do my better effort and try to follow all the best suggestions, but it has a limit, all of us have a way to work, to learn and do all things.

I don’t know if i’m perfectly clear, let me know.

I don’t agree with you mson77, we have to suggest the people don’t try to impose methods to think.

I’m wrong I apolige and maybe i’ll be out of the fórum also.

Have a nice week

Marcos
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266117 is a reply to message #264177] Sun, 09 September 2007 20:19 Go to previous messageGo to next message
BlackSwan
Messages: 25050
Registered: January 2009
Location: SoCal
Senior Member
Marcos,

If you do not like the timeliness, correctness, tone or tenor of ANY response, you are entitled to a full & complete refund of any & all monies remitted for this service.

With free advice, you get what you paid for it.

Would you prefer if all your questions were politely ignored?

You're On Your Own (YOYO)!
Re: Difference Between "Redo Log Buffer" and "Database Buffer Cache"? [message #266118 is a reply to message #266117] Sun, 09 September 2007 21:39 Go to previous message
mson77
Messages: 208
Registered: August 2007
Location: Brazil
Senior Member
Marcos,

peace please!
You are welcome. If you want to be out of this forum... it is up to you only.

Regarding your last message:

You said:
  • "Just give your Best suggestion and try to be friendly."
And I say:
Did you do the same at first mention about anacedent here?
--------------------------------------------------
You said:
  • "we have to suggest the people don’t try to impose methods to think."
And I say:
What are trying to do now? (No... you do not have to answer!)
--------------------------------------------------

Sincerely I am writing up here just to show that everyone is capable of think. But I will not spend any more second about this issue.
If you have a doubt that I can help you... you will have the information from me. The same I guess people of this forum will behave. But what you did not understand about anacedent message or even Michel Cadot message in this thread is: None is here to write summary of oracle manual content. If one needs information... I mean "secure and reliable" information... go to oracle manual. If you still have doubt or some topic is still unclear... post the message here and there will be many people wanting to explain clearly. But... the one MUST also do a favor to yourself first. Is it clear for you?
Also the one should always read the Forum Guide stick.

This is my own opinion and position... only!!
You are welcome to share and post your doubts here!
That's all. Now as anacedent said... YOYO. You decide.

Sincerely,


mson77
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