DB_BLOCK_SIZE and DB_FILE_MULTIBLOCK_READ_COUNT – What is Wrong with this Quote?

2 12 2010

December 2, 2010

(Forward to the Next Post in the Series)

It has been a couple of months since the last blog article that asked “What is Wrong with this Quote”, so I thought that I would try to add a couple of more blog articles to this series.  I recently reviewed the book “Oracle Tuning the Definitive Reference Second Edition”, but my review stopped when it extended to 24 pages (12 point Times New Roman font, 1 inch margins).   Why 24 pages?  It was probably just coincidence.

Page 531 of the book states the following:

“When multiple blocksizes are implemented, the db_block_size should be set based on the size of the tablespace where the large object full scans will be occurring.  The db_file_multiblock_read_count parameter is only applicable for tables/indexes that are full scanned.”

“With the implementation of multiple blocksizes, Oracle MetaLink notes that the db_file_multiblock_read_count should always be set to a value that sums to the largest supported blocksize of 32k.”

Examples are provided in the book that show that the value for the DB_FILE_MULTIBLOCK_READ_COUNT parameter multiplied by the value for the DB_BLOCK_SIZE parameter should always equal 32KB.  Thus, with a database block size of 16KB, the DB_FILE_MULTIBLOCK_READ_COUNT parameter value should be set to 2.

What, if anything, is wrong with the above quotes from the book?

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.

A Google search found similar information here: