| Inside Buffer Cache [message #476766] |
Sat, 25 September 2010 15:47  |
muktha_22
Messages: 527
Registered: December 2009
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Senior Member |
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Hi,
Share your thoughts:
(This is what I understand from 10g Concept pdf - B14220-02)
1) Soft Parsing and Cache Hit are the same meaning?
2) Soft Parsing are happening into the MRU not inside the LRU. Because the MRU only has the recently used Datablocks.
3) if so and the soft Parsing is doing some 'Update'. Then all the relevant Datablocks inside the MRU list will be marked as PINNED?
4) Or for the softparsing also the relevant Datablocks from MRU will be put back to the LRU and after work (Update, Delete..) it will be marked as Dirty buffer and ready to write to 'WRITE BLOCK'?
Thanks in advance
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| Re: Inside Buffer Cache [message #476784 is a reply to message #476780] |
Sun, 26 September 2010 01:13  |
muktha_22
Messages: 527
Registered: December 2009
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Senior Member |
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Hi Michel,
(Plz correct me where I'm wrong, so I can continue my reading with that point).
Eg - My Sql statement needed the datablock 1, 5.
1) Now those Datablocks are copied from the datafile to the Free buffer cache of LRU.
2) From there (In LRU), the particular data will be read from those Datablocks, and at this stage those blocks are marked as 'PINNED'. After the work done, those blocks will be moved into the end of MRU.
3) if any other user's Sql statements needed those Datablocks, that will be accessed from MRU, not in the LRU(Because it was already moved to MRU).
4) If the 2nd user's Sql statement is performing any UPDATE, DELETE..., will this be happened at the MRU area or anywhere else.
Thanks
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| Re: Inside Buffer Cache [message #476790 is a reply to message #476789] |
Sun, 26 September 2010 02:50 |
John Watson
Messages: 8964
Registered: January 2010
Location: Global Village
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Senior Member |
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Muktha, I've seen a few of your topics on this. The only interpretation I can place on your mis-understandings is that you are confusing PARSE with EXECUTE. You repeatedly describe a parse as reading blocks. As I suggested before, investigate the parse-bind-execute-fetch cycle. And either attend a course, or buy a suitable book. It seems as though the docs are not helping you.
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| Re: Inside Buffer Cache [message #476870 is a reply to message #476790] |
Mon, 27 September 2010 01:23 |
muktha_22
Messages: 527
Registered: December 2009
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Senior Member |
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Hi Michel,
1) In the above post I had asked what is the relationship b/w BUFFER CACHE and PGA? And u said no relationship.
But in you are another post (message #472315), U had written about PGA.
Can u tell me when PGA is being used along with Buffer Cache?
2) DBWn writes the data buffers back to the Datafile.
When DATAFILE being written back to the DATAFILES? (Not Buffer)
3) Hope when a single data got updated/deleted, the entire Datablock buffer will be
Written back to the DATAFILES. Why it needs to write back the entire Datablock, for a single change?
4) If a Data block present inside the Buffer Cache, so 'ALL THE DATA' of that entire Datablock can be used By any users. Am I right?
Thanks
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| Re: Inside Buffer Cache [message #476872 is a reply to message #476870] |
Mon, 27 September 2010 01:29 |
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Michel Cadot
Messages: 68732
Registered: March 2007
Location: Saint-Maur, France, https...
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Senior Member
Account Moderator |
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1)
Quote:But in you are another post (message #472315), U had written about PGA.
Post link (once more).
2)
Quote:When DATAFILE being written back to the DATAFILES? (Not Buffer)
Once again, your questions are cryptic or meaningless or irrelevant. What does this mean? You are not limited in the number of words you can post. So post questions in DETAILS, with links to what you read.
3) If you hope the whole block is written why do you ask why it does it? 
Once again this is explained in Database Concepts.
4)
Database Concepts
Regards
Michel
[Updated on: Mon, 27 September 2010 01:30] Report message to a moderator |
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