Azure SQL Database is upgrading the infrastructure for monitoring and alerts. This upgrade will improve stability and lay the foundation for enabling next-generation alerts. The upgrade will take place from January 22, 2019 to January 28, 2019.
During this upgrade, there will be no change to metric data and charts available in the Azure portal. However, customers who are using the Azure Monitor REST API will no longer be able to query for metric data written before December 21, 2018.
If you need metric data before December 21, 2018, please make a copy of the data before January 21, 2019. Moving forward, metric history will be built up to 93 days and maintained as such.