After an upgrade, thresholds for the upgraded Oracle Database Tablespace Alerts are set to null, disabling the alerts.

You must identify tablespaces in the database that are candidates for monitoring, and you must set the appropriate threshold values for these tablespaces.

Starting with Oracle Database 18c and later releases, in newly-created Oracle Database installations, the following values are used as defaults:

• 85% full warning

• 97% full critical