Oracle 11G OCP 1Z0-053 246

（246）The OPTIMIZER_USE_PLAN_BASELINES parameter is set to TRUE.

The optimizer generates a plan for a SQL statement but does not find a matching plan in the SQL plan baseline.

Which two operations are performed by the optimizer in this scenario? (Choose two.)

A. The optimizer adds the new plan to the plan history.

B. The optimizer selects the new plan for the execution of the SQL statement.

C. The optimizer adds the new plan to the SQL plan baseline as an accepted plan.

D. The optimizer adds the new plan to the SQL plan baseline but not in the ENABLED state.

E. The optimizer costs each of the accepted plans in the SQL plan baseline and picks the one with the lowest cost.

答案：（A、E）

解析：

OPTIMIZER_USE_SQL_PLAN_BASELINES = {true | false}

該引數決定是否使用儲存在SQL Management Base中的SQL plan baseline.

true, SQL語句被編譯的時候,優化器會檢視SQL plan baseline, 如果在SQL Management Base中找到了一個基線

則優化器會計算基線中每個執行計劃的成本,並選擇成本最低的一個

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