单选题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

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While tuning a SQL statement, the SQL Tuning Advisor finds an existing SQL profile for the statement that has stale statistics available. What would the optimizer do in this situation?（）

• A、It updates the existing SQL profiles with current statistics
• B、It makes the statistics information available to GATHER_STATS_JOB
• C、It initiates the statistics collection process by running GATHER_STATS_JOB
• D、It logs a warning message in the alert log so that the DBA can perform statistics collection manually

第3题：

Examine the command： SQL> DBMS_STATS.SET_TABLE_PREFS（’SH’， ’CUSTOMERS’， ’PUBLISH’， ’false’）；  Which statementdescribes 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

第4题：

You want to capture column group usage and gather extended statistics for better cardinality estimates for the CUSTOMERS table in the SH schema. Examine the following steps: 1. Issue the SELECT DBMS_STATS.CREATE_EXTENDED_STATS (‘SH’, ‘CUSTOMERS’) FROM dual statement. 2. Execute the DBMS_STATS.SEED_COL_USAGE (null, ‘SH’, 500) procedure. 3. Execute the required queries on the CUSTOMERS table. 4. Issue the SELECT DBMS_STATS.REPORT_COL_USAGE (‘SH’, ‘CUSTOMERS’) FROM dual statement. Identify the correct sequence of steps.（）

• A、3，2，1，4
• B、2，3，4，1
• C、4，1，3，2
• D、3，2，4，1

第5题：

Examine this command: SQL > exec DBMS_STATS.SET_TABLE_PREFS (‘SH’, ‘CUSTOMERS’, ‘PUBLISH’, ‘false’); Which three statements are true about the effect of this command?（）

• A、Statistics collection is not done for the CUSTOMERS table when schema stats are gathered.
• B、Statistics collection is not done for the CUSTOMERS table when database stats are gathered.
• C、Any existing statistics for the CUSTOMERS table are still available to the optimizer at parse time.
• D、Statistics gathered on the CUSTOMERS table when schema stats are gathered are stored as pending statistics.
• E、Statistics gathered on the CUSTOMERS table when database stats are gathered are stored as pending statistics.

第6题：

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.

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第14题：

While tuning a SQL statement, the SQL Tuning Advisor finds an existing SQL profile for the statement that has stale statistics available. What would the optimizer do in this situation?（）

• A、It updates the existing SQL profiles with current statistics.
• B、It makes the statistics information available to GATHER_STATS_JOB
• C、It initiates the statistics collection process by running GATHER_STATS_JOB
• D、It logs a warning message in the alert log so that the DBA can perform statistics collection manually.

第15题：

You are working in an online transaction processing (OLTP) environment. You use the FLASHBACKTABLE command to flash back the CUSTOMERS table. Before executing the FLASHBACK TABLE command, the system change number (SCN) was 663571. After flashing back the CUSTOMERS table, you realize that the table is not in the correct state. Now, you need to reverse the effects of the FLASHBACK TABLE command. Which is the fastest and the most efficient option to reverse the effects of the FLASHBACK TABLE command?（）

• A、Restore the backup control file and open the database with RESETLOGS option.
• B、Perform point-in-time recovery because flashback cannot be performed again on this table
• C、Execute the FLASHBACK DATABASE statement to retrieve the CUSTOMERS table as it was at SCN 663571
• D、Execute another FLASHBACK TABLE statement to retrieve the CUSTOMERS table as it was at SCN 663571

第16题：

You executed the following commands：   SQL> ALTER SESSION SET OPTIMIZER_USE_PENDING_STATISTICS = false； SQL> EXECUTE DBMS_STATS.SET_TABLE_PREFS（’SH’， ’CUSTOMERS’， ’PUBLISH’，’false’）； SQL> EXECUTE DBMS_STATS.GATHER_TABLE_STATS（’SH’， ’CUSTOMERS’）；   Which statement is correct regarding the above statistics collection on the SH.CUSTOMERS table in the above session？（）

• A、 The statistics are stored in the pending statistics table in the data dictionary.
• B、 The statistics are treated as the current statistics by the optimizer for all sessions.
• C、 The statistics are treated as the current statistics by the optimizer for the current sessions only.
• D、 The statistics are temporary and used by the optimizer for all sessions until this session terminates.

第17题：

You are working in an online transaction processing （OLTP） environment. You used the FLASHBACK TABLE command to flash back the CUSTOMERS table. Before executing the FLASHBACK TABLE command， the System Change Number （SCN） was 663571. After flashing back the CUSTOMERS table， you realize that the table is not in the correct state and the resultant changes are not what you had desired. So， you need to reverse the effects of the FLASHBACK TABLE command while ensuring that：  a） No other user data in the database is affected.  b） The operation takes the minimum possible time.  Which option would you choose？（）

• A、use the ROLLBACK command with SCN 663571
• B、perform Flashback Transaction Query with SCN 663571
• C、execute the FLASHBACK DATABASE statement to retrieve the CUSTOMERS table as it was at SCN 663571
• D、execute another FLASHBACK TABLE statement to retrieve the CUSTOMERS table as it was at SCN 663571

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