Step 9: Enter Maintenance Mode
To avoid unnecessary alerts during the upgrade process, enter maintenance mode on your cluster before you start the upgrade. Entering maintenance mode stops email alerts and SNMP traps from being sent, but does not stop checks and configuration validations. Be sure to exit maintenance mode when you have finished the upgrade to re-enable Cloudera Manager alerts. More Information.
On the Home > Status tab, click the actions menu next to the cluster name and select Enter Maintenance Mode.