[galaxy-dev] What is the correct place under Galaxy for a database that's created by a tool?

Hi folks, Hopefully this is a quick question. I'm working on a set of tools that will fire off a VM from within Galaxy and will then communicate with the VM. The VM will create a local database. The vision is that this won't be a shared database; in a shared Galaxy instance, each user will have his or her own database. What is the best place to create this database under the Galaxy file system? Thanks! Melissa