Maintain your Data Warehouse according to a schedule that is convenient and within your organization’s maintenance hours. All Data Warehouses have maintenance requirements to ensure that your Data Warehouse is up to date with latest updates and enhancements, however these updates could require Downtime and to ensure that your operation is not disrupted during critical load periods ensure that you follow the easy steps outlined in the following article.
https://techcommunity.microsoft.com/t5/Azure-Data-Warehouse-Support/Attempt-to-connect-to-server-fai...
Once you have configured your maintenance schedule ensure that you configure alerts to be kept up to date of your current resource status.
https://docs.microsoft.com/en-us/azure/azure-monitor/platform/alerts-metric#create-with-azure-portal
IMPORTANT NOTE
Azure DW instances which are DW400c and lower can complete maintenance outside of the designated maintenance window which could affect the Database availability
