When a CVM instance is used, it relies on a thread-local database which can be manually retrieved using [[local]].

The thread-local database can be set usint [[local-set]]. Originally, at thread initialization, it corresponds to
the [[global]] database which is common to all threads. Its value can also be altered using [[global-set]].

Ultimately, the [[global]] database itself returns [[default]] unless user has set its value to another database.

Default [[database]] is an Etch instance. See [[convex.db]].