Database Writer Parameters – What is Wrong with this Quote?

18 06 2010

June 18, 2010

While reading the June 2010 printing of the “Oracle Performance Firefighting” book I keep stumbling across interesting sections of the book.  Here is an interesting section – I hope that I did not exclude too much of the surrounding section of the book, causing the paragraph to lose contextual meaning (I am trying to balance how much typing I need to do with how much needs to be quoted to avoid losing the meaning of the material).  From page 219:

“From an Oracle perspective, I start thinking of any instance parameter that may increase Oracle’s IO writing efficiency. For example, I would investigate looking for a way to increase the database writer’s batch write size. As I mentioned, there are version-specific ways to alter the database writer’s batch size. Investigate the _db_block_write_batch and the _db_writer_max_writes parameters. Also considering increasing the instance parameter _db_writer_max_scan_pct (the default may be 40, for 40%) or _db_writer_max_scan_cnt, as they determine how many LRU buffer headers a server process will scan before it signals the database writer to start writing. Increasing these parameters provides more time for the write list to build up, and therefore results in more blocks written per database writer IO request.”

What, if anything, is wrong with the above quote from the book?  Keep in mind that these blog articles are intended to generate discussion – be sure to check any and all comments attached to the articles in this series.  The comment section is where the heart of the blog article material in this series will be found.

The point of blog articles like this one is not to insult authors who have spent thousands of hours carefully constructing an accurate and helpful book, but instead to suggest that readers investigate when something stated does not exactly match what one believes to be true.  It could be that the author “took a long walk down a short pier”, or that the author is revealing accurate information which simply cannot be found through other resources (and may in the process be directly contradicting information sources you have used in the past).  If you do not investigate in such cases, you may lose an important opportunity to learn something that could prove to be extremely valuable.


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