The Classic Query Engine (CQE) optimizer optimizes the query using the first partition member in the partitioned table. This access method is used to access rows from all of the partitions.
DB2® UDB Symmetric Multiprocessing feature data access methods cannot be used to access a partitioned table, but they can be used when processing temporary tables and for creating temporary indexes.
If the partitioned table is used in a query containing a subquery, the optimizer does not attempt to implement the query as a join composite query. This keeps the partitioned table from being materialized because of the join.