Greetz!
I am running Sharepoint 2010 Enterprise edition. I would like to create a maintenance database on the SQL instance on which my SharePoint databases are installed. I have read the article "Support for changes to the databases that are used by Office server products and by Windows SharePoint Services" (http://support.microsoft.com/kb/841057) and did not see that it was expressly forbidden to do this. The database would not be used so much that it would be competing for resources and work with it would largely be done off hours after the heaviest customer workload and prior to backups. No crawling would be done while it was in use either. But I have heard (from one person) that putting a db on a SharePoint sql instance is a frowned upon practice but no details were given to support why it shouldn't be done. I can see that a busy maintenance (or any) db, running all sorts of inquiries on the tables, etc, on a SharePoint server might compete for resources and that this could be an issue but for smaller jobs I don't see why it would be verboten. I would be using it mostly in place of using temp tables in my queries and for tables to store some baseline info.
This is one of those questions that are hard to form a good Google query on but I know there's SharePoint admins here who will have experience with this/
Thanks!
Even as a mother protects with her life
Her child, her only child,
So with a boundless heart
Should one cherish all living beings;