Very long Dimension build COMPILE step

Question

We're using AWM 11.2.0.1.0A and Oracle 11.2.0.1.0.
I have a time dimension called DAY with 7 levels from. The standard hierarchy contains all 7 levels, and I added a new hierarchy for the top 6 levels down to WEEK. The intention is that the hierarchies will be identical for the top 6 levels. There are 7420 dimension values (17 years) in total. When loading, the LOAD NO SYNCH step takes 5.2 seconds but the following COMPILE takes 22785 seconds (6h20m).
Can anyone shed any light on this?
Many thanks.

Answer 1

The COMPILE step of a TIME dimension does additional work over that of any other kind of dimension. Specifically it is precalculating a large number of value sets and self relations needed to support time calculations (year ago, moving average, etc.) This can be expensive when the time dimension gets large, but even so I am surprised at just how much time your case takes. (I should be clear that 7420 members counts as small for other kinds of dimensions -- I am only talking about time dimensions here.) I can only assume it is related to the depth of the hierarchies. If you don't need to use time based measures, then the simplest thing to do would be to redefine it as a user dimension. This may be worth trying as an experiment in any case since it would show whether or not it is time related.
Assuming you need it to be a true time dimension, then it may be useful to gather some more information. If you execute the following alter session before the build, then there will be some additional records in the CUBE_BUILD_LOG that break the COMPILE step down.
alter session set events='37377 trace name context forever, level 16384';
exec dbms_cube.build(' "DAY" USING (COMPILE) ')
Specifically you should see five new steps
COMPILE PARTITIONS
COMPILE HIERARCHIES
COMPILE ATTRIBUTES
COMPILE TIME OBJECTS
COMPILE GIDS
My guess is that the bulk of the time will be in COMPILE TIME OBJECTS, but I don't know for sure. It may also be worth raising a Service Request on this since then you could supply a reproducible test case.