Worldwide LHC Computing Grid (WLCG) is monitored by the distributed Service Availability Monitoring (SAM) framework, which sends test results through the Messaging infrastructure to the Central Data Warehouse at CERN. The main goal of the project was to improve the functionality of the Central Data Warehouse by writing some stress tests to monitor its behaviour through a Nagios system, detecting deficiencies (slow response, missing data, etc), notifying the service managers in an automated way and implementing solutions to the detected deficiencies. The report describes the SAM architecture and the implemented improvements of the Data Warehouse: gathering statistics of data load, new Nagios probes and purging mechanism.