Practice Question Answers and Explanations
- Correct answer: B
The combination of in-memory technology and multicore CPUs enabled real-time computing. Solid-state disks are still disks and relatively slow compared to memory. Multicore CPUs with large level 1 caches help, but also need in-memory technology.
- Correct answers: A, B
The advantages of columnar storage include improved compression and data-reading performance. (Because data is compressed, you can read more data at the same IO speed.) Improved data-writing performance is for row storage. Neither column nor row has improved performance when all fields are selected via SELECT *.
- Correct answer: B
Joining on key fields between tables in a dimension view will improve join performance. The answer “Use joins instead of unions for combining large data sets” has joins and unions swapped around: You should use unions rather than joins. Dynamic joins are created to improve performance. The word always makes the “Always use referential joins” answer wrong.
- Correct answers: A, B, D
The following are the correct performance techniques to improve join performance:
- Use unions instead of joins for combining large data sets.
- Always specify the cardinality of a join.
- Use left outer joins instead of right outer joins.
You should try to use only one table in an analytic view’s data foundation. The word always makes the “Always mark joins as dynamic” answer wrong.
- Correct answer: B
Implementing union pruning conditions will improve the performance of SAP HANA information views. You should not build a single large view; instead, build views up in layers. Use SAP HANA Live as an example. “Output as many fields as possible” is another way of saying “Use
SELECT *”; don’t do it. Instead, supply reporting tools with only the data they need right now, make them interactive, and use multiple small requests. - Correct answer: C
Breaking large statements into smaller steps will improve the performance of SAP HANA information views that include SQLScript. Do NOT use imperative logic,
SELECT *, or dynamic SQL if you need optimal performance. - Correct answers: B, C, E
The following are the performance techniques you can implement to improve the performance of SAP HANA information views:
- Minimize the transfer of data between execution engines.
- Investigate partitioning of large tables.
- Push down aggregations to SAP HANA.
“Calculation before aggregation” is reversed; to be correct, it should say “aggregation before calculation.” Filters should be applied as early as possible.
- Correct answer: A
- Correct answers: A, D
The Explain Plan tool shows the execution engines used and the list of operators.
- Correct answers: B, C
The Visualize Plan tool shows the number of records returned and the time taken in each step.
The Explain Plan tool shows the execution engines used, and the Administration Console shows the SQL Plan Cache.
- Correct answers: B, D
The Administration Console shows the SQL Plan Cache and the trace and log files. The Explain Plan tool shows the execution engines used. The Explain Plan and Visualize Plan tools show the operators used.
- Correct answers: B, D
Performance Analysis Mode shows the total number of records returned and the tables used.