Maximum number of schema elements
Datomic enforces the total number of schema elements to be fewer than 2^20, which includes schema attributes, value types and partitions. Attempts to create more than 2^20 schema elements will fail.
The :db namespace, and all :db.* namespaces, are reserved for use by Datomic. With the exception of :db/doc and :db/ident, you should not use Datomic attributes on your own entities.