IBM 000-8697 User Manual
How to Improve Performance
5-19
How Is Tuning Done?
How Is Tuning Done?
If the cached-read percentage is lower than 95 percent, you might be able to
improve performance by lowering the values of
improve performance by lowering the values of
LRU_MAX_DIRTY
and
LRU_MIN_DIRTY
to increase the number of free and/or unmodified pages
that are available in the shared-memory
LRU
queues.
If the cached-write percentage is lower than 82 percent, you might be able to
improve performance by increasing the
improve performance by increasing the
LRU_MAX_DIRTY
and
LRU_MIN_DIRTY
values. This increases the number of modified buffers that
are able to accumulate in the
MLRU
queue and increases the likelihood that
pages will be reused before they are written to disk.
To change the value of either of these parameters, edit the configuration file
using an operating system editor.
using an operating system editor.
The optimal value of
CLEANERS
depends on your specific hardware config-
uration. The maximum value of
CLEANERS
is 32. The minimum value is 0.
When
CLEANERS
is set to 0, the tbinit daemon assumes all responsibility for
page cleaning.
You might want to configure a page cleaner for each separate physical device.
However, if more than one disk shares a controller channel, you might find
that more than three page cleaners per controller overburdens the controller.
In most cases, the additional cleaners do not improve performance unless
you separate successive chunks from a blobspace or dbspace on the disk.
Ideally, you should try to assign successive chunks to separate disk devices.
(Refer to
However, if more than one disk shares a controller channel, you might find
that more than three page cleaners per controller overburdens the controller.
In most cases, the additional cleaners do not improve performance unless
you separate successive chunks from a blobspace or dbspace on the disk.
Ideally, you should try to assign successive chunks to separate disk devices.
(Refer to
for more details about disk layout. Refer to
for
more details about how to change the number of page cleaners.)
The default value of
LRUS
is the larger of
USERS
/2 or 8, where
USERS
is the
specified configuration file parameter. The minimum value of LRUS is 3 and
the maximum value is 8. The optimal value of
the maximum value is 8. The optimal value of
LRUS
depends on your specific
hardware configuration. Your best guide for selecting a value for
LRUS
is to
experiment with different values and monitor the performance benefits. You
might find that a larger value increases performance on machines with more
than two
might find that a larger value increases performance on machines with more
than two
CPU
s. To change the value of
LRUS
, edit the configuration file using
an operating system editor.