User yyy will need appropriate privledges necessary to create the objects.
See: privileges required to import objects into your own schema.
http://docs.oracle.com/cd/E11882_01/server.112/e22490/original_import.htm#BABFHCBI
Also:
http://docs.oracle.com/cd/E11882_01/server.112/e22490/dp_overview.htm#CJAIBFJG
Many Data Pump Export and Import operations require the user to have the DATAPUMP_EXP_FULL_DATABASE role and/or the DATAPUMP_IMP_FULL_DATABASE role. These roles are automatically defined for Oracle databases when you run the standard scripts that are part of database creation. (Note that although the names of these roles contain the word FULL, these roles are actually required for all export and import modes, not only Full mode.)
The DATAPUMP_EXP_FULL_DATABASE role affects only export operations. The DATAPUMP_IMP_FULL_DATABASE role affects import operations and operations that use the Import SQLFILE parameter. These roles allow users performing exports and imports to do the following:
•Perform the operation outside the scope of their schema