OCP 1Z0 052 40

40. You have statistics collected for some selected tables. Your requirement  is  that  the statistics for the 
tables and all dependent  indexes must not be overwritten by  further statistics collection until a certain 
point of time. 
How would you achieve this? 
A.Lock statistics for the tables. 
B.Change STALE_PERCENT to zero for the tables. 
C.Set the TIMED_STATISTICS parameter to TRUE. 
D.Set the STATISTICS_LEVEL parameter to BASIC. 
E.Set the OPTIMIZER_USE_PENDING parameter statistics to TRUE. 
Answer: A

B 

STALE_PERCENT - Determines the percentage of rows in a table that have to change before the statistics on that table are deemed stale and should be regathered. The valid domain for stale_percent is non-negative numbers.The default value is 10%. Note that if you set stale_percent to zero the AUTO STATSgathering job will gather statistics for this table every time a row in the table is modified.




C 与表的statistics收集无关

TIMED_STATISTICS specifies whether or not statistics related to time are collected.

Values:

• true

  The statistics are collected and stored in trace files or displayed in the V$SESSTATS and V$SYSSTATS dynamic performance views.

• false

  The value of all time-related statistics is set to zero. This setting lets Oracle avoid the overhead of requesting the time from the operating system.

D 当设置为basic时不会自动收集，但还是可以手动收集的

STATISTICS_LEVEL specifies the level of collection for database and operating system statistics. The Oracle Database collects these statistics for a variety of purposes, including making self-management decisions.

The default setting of TYPICAL ensures collection of all major statistics required for database self-management functionality and provides best overall performance. The default value should be adequate for most environments.

When the STATISTICS_LEVEL parameter is set to ALL, additional statistics are added to the set of statistics collected with the TYPICAL setting. The additional statistics are timed OS statistics and plan execution statistics.

Setting the STATISTICS_LEVEL parameter to BASIC disables the collection of many of the important statistics required by Oracle Database features and functionality

E

OPTIMIZER_USE_PENDING_STATISTICS specifies whether or not the optimizer uses pending statistics when compiling SQL statements.