OCP-1Z0-053-V13.02-209题

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209.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. Answer: A 答案解析: 参考:http://docs.oracle.com/cd/E11882_01/server.112/e41573/stats.htm#PFGRF94725 By default, the optimizer uses the published statistics stored in the data dictionary views. If you want the optimizer to use the newly collected pending statistics, then set the initialization parameter OPTIMIZER_USE_PENDING_STATISTICS to TRUE (the default value is FALSE), and run a workload against the table or schema: ALTER SESSION SET OPTIMIZER_USE_PENDING_STATISTICS = TRUE;

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