Automated SP_WhoIsActive SQL Activity Capturing Issue I have an SQL Agent Job on a production server that keeps failing with the below messages. It is supposed to be capturing SQL Server activity using the SP_WHOISACTIVE stored proc, at regularly scheduled intervals.


  Executed as user:  Warning: Null value is eliminated by an aggregate
  or other SET operation. [SQLSTATE 01003] (Message 8153)  
  
  Warning: Null value is eliminated by an aggregate or other SET
  operation. [SQLSTATE 01003] (Message 8153)  
  
  Warning: Null value is eliminated by an aggregate or other SET
  operation. [SQLSTATE 01003] (Message 8153)  
  
  Violation of PRIMARY KEY constraint 'PK_WhoIsActive'. Cannot insert
  duplicate key in object 'monitoring.WhoIsActive'. The duplicate key
  value is (Jan 20 2017  8:25AM, 109). [SQLSTATE 23000] (Error 2627)  
  
  The statement has been terminated. [SQLSTATE 01000] (Error 3621).  
  
  The step failed.


Any idea what may be causing this?

What steps should I follow to fix this error?
It appears from the Primary Key name that you are running Adam Machanic's sp_WhoIsActive and storing the result in a table.
If that is the case, the warnings are normal and caused by the options you set when calling sp_WhoIsActive. The Primary Key violation is what is causing the job to fail.  Take a look at the definition of the primary key.
I believe you will find that the Primay Key needs to be changed in order to insure uniqueness.
In my implementations for this I leave the table as a heap and do not define a primary key on this table. I only keep a few days of data in the table and do not use it for replication.
Here is an article on how to implement it:
Brent Ozar Implementation of sp_WhoIsActive