CONTEXT: When you remove a machine from monitoring in SQL Monitor / delete a database from an instance / rename a database... - data stays in the SQL Monitor database (e.g. machine/instance/database is still visible on the Analysis tab), at least until relevant monitoring data is purged.

PROBLEM: If you have some purge settings set to "do not purge", that data never goes away. Sometimes that is OK (you want the history retained), sometimes it's not (bloats the SQL Monitor database, unneeded entries on the Analysis page...).

EXAMPLE SOLUTIONS:
Add options to manually (on demand) delete data for a chosen combination:
- machine (+ all instances & databases on it)
- machine + instance (+ all databases on it)
- machine + instance + database