I read that persistent object types are stored in repository ,while other is not .Please tell me about this ,and is there any documentation available regarding this.
All the details are at content server fundamentals guide
From CS Fundamentals Guide
Persistence
Most object types are persistent. When a user creates an object of a persistent type, the object is stored in the repository and persists across sessions. A document that a user creates and saves one day is stored in the repository and available in another session on another day. The definitions of persistent object types are stored in the repository as objects of type dm_type and dmi_type_info.
There are some object types that are not persistent. Objects of these types are created at runtime when they are needed. For example, collection objects and query result objects are not persistent. They are used at runtime to return the results of DQL statements. When the underlying RDBMS returns rows for a SELECT statement, Content Server places each returned row in a query result object and then associates the set of query result objects with a collection object. Neither the collection object nor the query result objects are stored in the repository. When you close the collection, after all query result objects are retrieved, both the collection and the query result objects are destroyed.
