Oracle lets you perform parallel queries with objects and objects synthesized in views, when you follow these rules:
To make queries involving joins and sorts parallel (using the ORDER BY, GROUP BY, and SET operations), a MAP function is required. In the absence of a MAP function, the query automatically becomes serial.
Parallel queries on nested tables are not supported. Even if there are parallel hints or parallel attributes for the table, the query is serial.
Parallel Insert Direct Load (PIDL) and Parallel Create Table As Select (PCTAS) are supported on varray and ADT columns. The ADT columns must meet the following characteristics:
type is final
ADT attributes, at any level within the main type is final
lob/varray/xmltype attributes are stored as securefile
all other attributes are simple scalars
Rest of the DML and DDL are always performed in serial.
Parallel DML is not supported on views with INSTEAD-OF trigger. However, the individual statements within the trigger may be parallelized.