 | Oracle Consulting Tips by Burleson |
The dirty buffers inspected Oracle metric is the number of dirty buffers found by the foreground while the foreground is looking for a buffer to reuse.
A dirty buffer is a buffer whose contents have been modified. Dirty buffers are freed for reuse when DBWR has written the blocks to disk.
The database buffer cache is organized in two lists: the write list and the least-recently-used (LRU) list. The write list holds dirty buffers, which contain data that has been modified but has not yet been written to disk. The LRU list holds free buffers, pinned buffers, and dirty buffers that have not yet been moved to the write list. Free buffers do not contain any useful data and are available for use. Pinned buffers are buffers that are currently being accessed.
My notes on dirty buffer (DBWR) tuning include:
Oracle documentation also states that when attempting to view the dirty buffers inspected, "Some statistics are populated only if the TIMED_STATISTICS initialization parameter is set to true. Those statistics are flagged in the right-hand column"
This, and many other Oracle performance metrics are discussed in my book "Oracle Tuning" by Rampant TechPress. You can buy it directly from the publisher and save 30% at this link:
http://www.rampant-books.com/book_1002_oracle_tuning_definitive_reference_2nd_ed.htm
