Examine the initialization parameters for a database an OLTP overload.
What is the effect of changing the value of the parameter?
A.
It influences the optimizer to always use the value of the parameter?
B.
It influences the optimizer to use indexes instead of full table scans as the estimated cost of the
using index is reduced.
C.
It influences the optimizer to use full table scans instead of index scans as the estimated cost of
full table scan is reduced.
D.
It influenced the optimizer to use bitmap indexes as the estimated cost conversion from bimap
is rowed us reduced.
Explanation:
OPTIMIZER_INDEX_COST_ADJ
OPTIMIZER_INDEX_COST_ADJ lets you tune optimizer behavior for access path selection to be
more or less index friendly—that is, to make the optimizer more or less prone to selecting an index
access path over a full table scan.
The default for this parameter is 100 percent, at which the optimizer evaluates index access paths
at the regular cost. Any other value makes the optimizer evaluate the access path at that
percentage of the regular cost. For example, a setting of 50 makes the index access path look half
as expensive as normal.
I’m agree.
For me C is correct. Before ALTER SESSION value of parameter is 0, and after is 50. It means that it is increased and cost of index usage is bigger.
Rafal ,
I think , answer should be B not C as default value should be 100 and values is 50 which is less here and optimizer select access path go for index scan rather than full table scan
mistake on screen, VALUEs must be raised by one position:
optimizer_mode ALL_ROWS
optimizer_index_cost_adj 100
correct answer C, before ALTER SESSION value is 100
sorry, B