1. A method of managing a directory for a database system having an in-memory database and a plurality of permanent memory-based databases, comprising: receiving a user request to access a database object stored in a permanent memory-based database; in response to receiving the user request, performing a first search of the in-memory database to determine when the requested database object is also stored in the in-memory database; in response to receiving the user request, performing a second search of a directory for database objects in the plurality of permanent memory-based databases comprising a plurality of directory entries to determine when a directory entry exists in the directory for the requested database object, wherein each directory entry in the directory corresponds to one of a plurality of stored database objects stored in the permanent memory-based databases and indicates a location from which to access that stored database object including one of a specific permanent memory-based database containing the stored database object and the in-memory database; in response to the first search determining that the requested database object is also stored in the in-memory database and the second search determining that a directory entry exists for the requested database object and indicates the specific permanent memory-based database, modifying the directory entry in the directory for the requested database object to indicate that the requested database object is to be accessed in the in-memory database; in response to the first search determining that the requested database object is also stored in the in-memory database and the second search determining that no directory entry exists in the directory for the requested database object, creating a directory entry in the directory for the requested database object to indicate that the requested database object is to be accessed in the in-memory database; and accessing the requested database object from the in-memory database in response to the corresponding directory entry for the requested database object indicating the in-memory database.