The quick fix is via SharePoint PowerShell – open that and do the following step.
NOTE: You must be an Admin to do this. Run your SharePoint PowerShell as Administrator.
Step 1 – Get the GUID of the Service Application
> Get-SPServiceApplication
…
Managed Metadata … Managed Metadata … 50f28d03-a89a-4cd0-a5ce-3fa95bf19ac7
Web Analytics Ser… Web Analytics Ser… ec65ee1c-f3d3-4bc7-9bb1-6cccb4705cdf
Excel Services Ap… Excel Services Ap… 4041c849-5ca9-48e1-93a6-1a7b4edac13f
…
Notice the Web Analytics service – copy the GUID in the ID Column.
Step 2 – Turn on Data Trimming on the Reporting Service
> Set-SPWebAnalyticsServiceApplication -Identity <GUID> -EnableDataTrimming
(replace <GUID> with the GUID you copied above – NOTE: if you only have one Analytics Service, you can omit the GUID)
for example:
> Set-SPWebAnalyticsServiceApplication -Identity ec65ee1c-f3d3-4bc7-9bb1-6cccb4705cdf -EnableDataTrimming
Give if a few minutes to let the SPTimer job kick then return to the Health Monitor, click the message and select Re-analyze Now – message should go away!