You have been asked to assess if using column store compression (previously known as
hybrid columnar compression or HCC) would help improve the performance of queries on
some large tables. Which three aspects should you consider before you choose this
compression method?(Choose three.)
A.
Check whether direct path load operations are used to insert rows in the table.
B.
Check whether the table is frequently queried using fulltablescans as column store
compression only minimizes I/O during full table scans.
C.
Check whether the table is frequently updated because it will have overhead for insert
and update operations.
D.
Check whether the table has LOB columns as it will minimize I/O for the queries.
E.
Check whether the table blocks aresparselypopulated as this will defragment the blocks.
imo, A, B, C, correct.
D – wrong
Hybrid Columnar Compression is designed for relational data, not for unstructured data in BLOBs (or CLOBs). LOBs are best stored in the Oracle Database as SecureFiles LOBs , and if the customer has licensed the Advanced Compression Option, they can use SecureFiles Compression and Deduplication to potentially reduce the amount of
storage required for LOBs.
http://www.oracle.com/technetwork/database/exadata/ehcc-twp-131254.pdf
A,B,C
I think B,C and D are correct.
for A. Direct path load – I think if data is loaded using direct path then its good for HCC in aspect of saving storage but as in Question mention what aspect we need to check I think we should check if table have LOB or not if its have LOB there is no meaning to have HCC as per doc http://www.oracle.com/technetwork/database/exadata/ehcc-twp-131254.pdf
@vasya please let me know if I am wrong.
ABC
ACD
Where A encourages the usage of HCC while C & D do not! So, those are good aspects to consider when you implement HCC!
B is wrong as it clearly says “only minimizes I/O during full table scans” why ONLY?!
E does not matter so it is out of context!
in the exam I chose A,C,D. I think that I made a mistake by choosing the option “D”
imo A,C,E
http://www.oracle.com/technetwork/database/exadata/ehcc-twp-131254.pdf
Confusing question but I would pick A,C,D. Most of the answers already hinted in the documentation except B. The way I understand about D is different than Vasya. DBA should check if the column has LOB or it will not be efficiency as the document suggested.
B is not relevant. E – not relevant.