An index called ORD_CUSTNAME_IX has been created on the CUSTNAME column in the
ORDERS table using the following command:
SQL>CREATE INDEX ord_custname_ix ON orders (custname);
The ORDERS table is frequently queried using the CUSTNAME column in the WHERE
clause. You want to check the impact on the performance of the queries if the index is not
available. You do not want the index to be dropped or rebuilt to perform this test.
Which is the most efficient method of performing this task?
A.
disabling the index
B.
making the index invisible
C.
making the index unusable
D.
using the MONITORING USAGE clause for the index
Explanation:
Invisible Indexes
An invisible index is maintained by Oracle Database for every data manipulation language
(DML) statement, but is ignored by the optimizer unless you explicitly set the parameter
OPTIMIZER_USE_INVISIBLE_INDEXES to TRUE on a session or system level.
Making an index invisible is an alternative to making it unusable or dropping it. Using
invisible indexes, you can:
Test the removal of an index before dropping it
Create invisible indexes temporarily for specialized, nonstandard operations, such as online
application upgrades, without affecting the behavior of existing applications
For more information, see Oracle Database Administrator’s Guide.