request is eligible for IPE but does not meet thresholds

Database

request is eligible for IPE but does not meet thresholds

In TD14.10, I’m running an explain on a query and I’m getting the message “This request is eligible for incremental planning and execution (IPE) but does not meet thresholds. The following is the static plan for the request.”  I am surprised that the query does not meet cost thresholds because it is a sizable/expensive query.  Part of the reason the query is so expensive is because it is NOT using DPE.  The value range for the partitioning column is derived from a non-correlated scalar subquery which, if I understand correctly, should allow the optimizer to use IPE.  Also, when I replace the scalar subqueries with hard-coded values, the cost of the query is reduced significantly.  I thought I understood the meaning of that explain message “This request is eligible for (IPE) but does not meet thresholds”, but maybe I’m overlooking some caveat.  I want to run a test to prove that IPE is, in fact, working properly on my TD14.10 system, when the conditions are right.  Toward that end, I have three questions:

1. If I get the explain message “This request is eligible for (IPE) but does not meet thresholds”, does that *prove* that IPE is enabled on my system?

2. Assuming the answer to the preceding question is YES, what *exactly* does the phase “but does not meet thresholds” mean?  Does it mean the cost of the static plan is not high enough to consider IPE – or – does it mean the cost of the dynamic plan (when using IPE) does not show big enough improvement over the static plan, therefore IPE is not used?

3. Is there a way to adjust the cost threshold low enough (as a test) to persuade the optimizer to use IPE?  If so, how?  Also, can it be done via a diagnostic? 

Lastly, here are some pertinent dbscontrol settings for my TD14.10 system:

SecureExplain = 0

CostProfileId = 0

EnableSetCostProfile = 1  (Enabled)

It is my understanding that the system’s default Cost Profile for my TD14.10 (Linux) system is “T2_TD13_0_LINUX64 - Default Type 2 formula parameter initialization values for TD13 on 64 bit Linux platforms.”