OCP 1Z0 052 42

42. Examine the command:

SQL> DBMS_STATS.SET_TABLE_PREFS('SH', 'CUSTOMERS', 'PUBLISH', 'false');

Which statement describes the effect of the above command?

A.Automatic statistics collection is stopped for the CUSTOMERS table.

B.Statistics for the CUSTOMERS table are locked and cannot be overwritten.

C.Existing statistics for the CUSTOMERS table become unusable for the query optimizer.

D.Subsequently, statistics gathered on the CUSTOMERS table are stored as pending statistics.

Answer: D

Pending Statistics

The package gather statistics and stores it in the dictionary by default. User's can store these statistics in the system's private area instead of the dictionary by turning the

PUBLISH

option to

FALSE

using
the

SET*PREFS

procedures. The default value for

PUBLISH

is

TRUE

.The statistics stored in private area are not used by Cost Based Optimizer unless parameter

optimizer_use_pending_statistics

is
set to

TRUE

. The default value of this parameter is

FALSE

and this boolean parameter can be set at the session/system level. Users can verify the impact of the new statistics on query
plans by using the pending statistics on a session.