IBM 000-8697 Manual Do Utilizador

How to Improve Performance

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

 and

 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:

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

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 of modified buffers in the queue,
which when reached initiates page-cleaning activity (as
idle writes)

LRU_MIN_DIRTY

The threshold percentage of modified buffers in the queue,
which when reached indicates the point at which page-
cleaning activity can be suspended