Examine the exhibit.
Correct Answer: E
Explanation/Reference:
PX BLOCK ITERATORThis operation is typically the first step in a parallel pipeline.
The BLOCK ITERATOR breaks up the table into chunks that are processed by each of the parallel servers involved.
Incorrect:
B, C: The scan on the Departsments table is done in parallel.
Note:
*As per exhibit: Line 7 is run first, followed by line 6.
*
Example with same structure of execution plan:
Here’s how to read the plan:1. The first thing done is at line 9 - an index fast full scan on SYS.OBJ$.I_OBJ1 index. This is done in parallel, as indicated from the “PX SEND” line above.2. In line 8, we’re doing a “PX SEND BROADCAST” operation. When joining tables in parallel, Oracle can choose to either broadcast results (rows) from one operation to apply to the other table scan, or it can choose PX SEND HASH. In this case, our CBO determined that a BROADCOAST was appropriate because the results from the OBJ$ table were much lower than the MYOBJ table3. Line 7, the PX RECEIVE step, is basically the consumer of the broadcasted rows in step 84. Line 6 is an in-memory BUFFER SORT of the rows returned from the index scan on OBJ$5. Lines 11 and 10, respectively, indicate the full scan and PX BOCK ITERATOR operation for the granules involved in the 8 PQ servers6. In line 5, Oracle is doing a hash join on the resulting rows from the parallel scans on MYOBJ and OBJ$7. Line 4 is a per-PQ server sort of data from the joind PQ servers8. Line 3 is the consumer QC that holds the result of the each of the PQ servers9. Line 2 is the PX Coordinator (QC) collecting, or consuming the rows of the joined data10. Line 1 is the final SORT AGGREGATE line that performs the grouping function
