The "Oracle Database Tablespace Monthly Space Usage" in EM 12c shows no data when I run it for a cluster instance.
Single databases works ok.
Another strange thing is that I don't get the option to choose the cluster database in my "target" list when I try to run this report - only the instance names.
Please do a 'Create like' of 'Oracle Database Tablespace Monthly Space Usage' report.
Now provide 'Target Type' as 'Cluster Database' and create the report.
Now run the report against cluster database. This will resolve the issue.