I was going through two monitor elements of DB2 pool_drty_pg_thrsh_clns(dirty pages thresold cleaner) and pool_drty_pg_steal_clns(Dirty pages steal cleaner). what i dont understand is when u have thresold cleaner ,how DB2 reaches to the point where it has to steal some victim pages. for eg: if I have 1 GB of bufferpool and changed pages thresold DB parameter is set to 60% then it should always trigger when the bufferpool has 600MB of dirty pages, it should not allow to the point where the whole bufferpool is of dirty pages and it has to stea some pages.
Am I missing something here? please let me know ur views.

You have a misunderstanding of what the monitor element is. Here is the definition:

The number of times a page cleaner was invoked because a synchronous write was needed during the victim buffer replacement for the database.

Basically this means that a page cleaner, which is asynchronous, that was busy doing its thing was needed because of a synchronous write.

Andy