Database Reference
In-Depth Information
•
Query Begin
(
9
)/
Query End
(
10
): These are raised at the start and end of
query evaluation. They usually contain only one interesting subclass event:
°
MDXQuery
(
0
): This shows the MDX statement sent to Analysis
Services. For the
Query
End
event, the
Duration
column shows the
overall amount of time taken to run the query and return its results
back to the client.
•
Calculate Non Empty Begin
(
72
)/
Calculate Non Empty End
(
74
):
These have no related subclass events. The
Calculate
Non
Empty
events are
raised when Analysis Services performs non-empty filtering operations, for
example, when the
NonEmpty
MDX function or the
Non Empty
statement
is used in a query, and these operations are often the cause of slow query
performance. When the value of the
Duration
column for
Calculate
Non
Empty
End
is large, we should check the
IntegerData
column to see if it bulk
mode is being used or not. When the value of
IntegerData
is
11
, Analysis
Services iterates over all the tuples in a set to perform non-empty filtering,
and this can be very slow. For all other
IntegerData
values (usually
1
),
Analysis Services is operating in bulk mode, which is usually much faster.
•
Execute MDX Script Begin
(
78
)/
Execute MDX Script End
(
80
): These
have no related subclass events. They are raised at the beginning and end
of the evaluation of the MDX Script on a cube, which is usually a very quick
operation. However, if there are any complex named sets defined on the cube
then MDX Script evaluation can take a long time.
•
Get Data From Aggregation
(
60
): This has no related subclass events. This
event is raised when the Storage Engine reads data from an aggregation.
•
Get Data From Cache
(
61
): This is raised when data is read from cache.
There are several subclass events that identify the type of cache used. This
event will be seen very frequently on a production server, because after a
query has been run, all of the data it returns should be kept in cache. If this
is not the case, it usually indicates that either there is not enough memory
available for caching, or that calculations have been written so that the values
they return cannot be cached. The subclass events are as follows:
°
Get data from measure group cache
(
1
)
°
Get data from flat cache
(
2
)
°
Get data from calculation cache
(
3
)
°
Get data from persisted cache
(
4
)
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