Hi,
Whenever any changes has to be written to Online Redo log files, that has to be done in the memory; where does that happen. Does it happen somewhere in OS buffers
Regards
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Hi,
Whenever any changes has to be written to Online Redo log files, that has to be done in the memory; where does that happen. Does it happen somewhere in OS buffers
Regards
redo log buffer in SGA. LGWR writes from redo log buffer to redo log file.
The following could be useful...
http://otn.oracle.com/docs/products/...inere.htm#3848
HTH.
Do u mean to say it reads the blocks and puts in log buffer and does the modification.......and again writes them back to disk......?
Hi, you seem to be mixing it up with the database buffer cache(db_block_buffer) in the SGA. The needed database blocks are in this database buffer cache. Whereas, the redo log buffer has the changes made to this database blocks in the database buffer cache.
Check this out...
http://otn.oracle.com/docs/products/...intro.htm#7179
Hope this clears it out.
Hello....hth,
What i am telling is, any data that has to be wrtten to the file it has to be done in the memory...right...forget abt oracle......any software for that matter............
So for datafiles we have buffer cache....
in the same way, for writing into online redo logfiles it has to be done in the memory...right....so where in the memory.....
REDO LOG BUFFER IN THE MEMORY.Quote:
Originally posted by Sonia
in the same way, for writing into online redo logfiles it has to be done in the memory...right....so where in the memory.....
Cheers.
P.S.: It would do you good if you could read throu' the links I posted. In the 2nd link, there is a very good pictorial representation of what we are discussing.
who will read the blocks from Redolog file to the redo log buffer ?
As Oracle 9i Administrator Guide said, Redo file are filled with redo records, each of which is a description of a change made to a single block in the database. How does Logminer reconstruct the DML statement in SQL_REDO?
Nobody. Why should anybody do that?Quote:
Originally posted by Sonia
who will read the blocks from Redolog file to the redo log buffer ?
Done, it will reconstructe one statement for every record changed.Quote:
Originally posted by Calvin_Qiu
How does Logminer reconstruct the DML statement in SQL_REDO?
what are you tallking about?Quote:
Originally posted by Sonia
who will read the blocks from Redolog file to the redo log buffer ?
Hi Sonia
I think you are completely confused about the working of the redo log buffer, LGWR and online redo logs. Refer the online help that comes with Oracle software. This will clear most of your doubts. Anyhow let me try to explain something
As users perform transactions (updates, inserts, deletes), the redo buffer (a part of the oracle SGA in MAIN MEMORY) fills up. After that, based on certain conditions like a timeout or commit the redo buffer entries are written from the redo buffer to the online redo logs (on DISK) by an Oracle background process called LGWR. Once the online redo logs are filled, they may or may not be archived based on the mode in which your database is operating.
Burzin.
Right, forget about oracle, any software for that matter - how could any write operation ever be done in memory???? (Of course, disk controlers write cache does not count here.)Quote:
Originally posted by Sonia
[B]What i am telling is, any data that has to be wrtten to the file it has to be done in the memory...right...forget abt oracle......any software for that matter............
Changes are performed in memory, physical writes must allways be performed on disk. Writes are permanent operations, it means changes are permanently stored somewhere where they are safe - RAM is certainly not such media.
There is no such thing as "write to file performed in memory".