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How to Improve Performance 5-17
Page-Cleaner Parameters
Page-Cleaner Parameters
In the discussion of page-cleaning tuning, it is especially true that your
hardware configuration and your application influence the values that are
best for your environment.
Familiarize yourself with the OnLine approach to page cleaning before you
begin this section. Refer to page 2-57 and page 2-58 for background infor-
mation about the
LRU queues and their role in the page-cleaning process.
You can tune four page-cleaning parameters to affect performance:
Efficient Page Cleaning
Traditionally,the effectiveness of page-cleaner activity has been measured by
the different types of writes performed. Idle writes occur when the page
cleaners wake by themselves to flush the LRU queues. Foreground writes occur
if the database server process must initiate page flushing. (Refer to page 2-75
for a description of the different types of writes that occur during OnLine
operation.) You can examine the types of writes that occur in your
environment by executing tbstat -F.
CLEANERS
The number of page cleaners
LRUS
The number of LRU queue pairs
LRU_MAX_DIRTY
The threshold percentage ofmodified buffers in the queue,
which when reached initiates page-cleaning activity (as
idle writes)
LRU_MIN_DIRTY
The threshold percentage ofmodified buffers in the queue,
which when reached indicates the point at which page-
cleaning activity can be suspended