There is some good advice and queries for generating reports on this in the following article.
For example, if you want to see the most used reports, you can do the following:
SELECT COUNT(Name) AS ExecutionCount,
Name,
SUM(TimeDataRetrieval) AS TimeDataRetrievalSum,
SUM(TimeProcessing) AS TimeProcessingSum,
SUM(TimeRendering) AS TimeRenderingSum,
SUM(ByteCount) AS ByteCountSum,
SUM([RowCount]) AS RowCountSum
FROM (SELECT TimeStart,
Catalog.Type,
Catalog.Name,
TimeDataRetrieval,
TimeProcessing,
TimeRendering,
ByteCount,
[RowCount]
FROM Catalog
INNER JOIN
ExecutionLog
ON Catalog.ItemID = ExecutionLog.ReportID
WHERE Type = 2
) AS RE
GROUP BY Name
ORDER BY COUNT(Name) DESC,
Name;
One thing to note is that by default the execution log will only keep 2 months worth of data. You can control this behaviour with the ExecutionLogDaysKept
server property, see this technet article.