103.Observe the following PL/SQL block:

BEGIN

dbms_spm.configure('SPACE_BUDGET_PERCENT', 30);

END;

Which statement is correct regarding the above PL/SQL block?

A. It automatically purges the SQL management objects when SMB occupies more than 30% of the

SYSAUX tablespace.

B. It reserves 30% of the space in the SYSAUX tablespace for SQL Management Base (SMB).

C. It reserves 30% of the space in the SYSTEM tablespace for SMB.

D. It generates a weekly warning in the alert log file when SMB occupies more than 30% of the SYSAUX

tablespace.

Answer: D

答案解析：

When the space occupied by SQL management base exceeds the defined space budget limit, a weekly database alert is generated.

Table 136-6 Names & Values for CONFIGURE Procedure Parameters

Name	Description	Possible Values	Default Value
space_budget_percent	Maximum percent of SYSAUX space that can be used for SQL management base	1,2, …, 50	10
plan_retention_weeks	Number of weeks to retain unused plans before they are purged	5,6, …, 523	53

[email protected]> begin   2  dbms_spm.configure('SPACE_BUDGET_PERCENT',30);   3  END;   4  / PL/SQL procedure successfully completed.

    DBMS_SPM包允許使用者使用SQL計劃管理功能來管理SQL執行計劃，SQL計劃管理功能可以通過長時間的記錄和分析SQL語句執行計劃來有效的防止由於突然間更改一個SQL語句執行計劃所導致資料庫效能的衰退，而且還可以通過已知的一組高效的執行計劃生成一些執行計劃基線。這些SQL計劃基線能夠隨後用於保證適當的效能，即使是在系統發生改變的時候，通常在如下的情況  使用SQL計劃功能來管理SQL執行計劃：
    資料庫升級安裝改變優化器時，通常會有少部分的執行計劃改變，大部分可能是有變化的或者是有提高的。無論怎樣，還是存在一部分的計劃改變所導致效能的衰退問題。此時利用SQL計劃基線能顯著地減少由於資料庫更新帶來的效能問題。
    正在執行的系統和不斷變化的資料會帶來一些效能問題。利用SQL計劃基線可以減少效能回退同時可以維持系統穩定。
    有時部署新的系統模組相當於引用新的SQL語句到系統中，應用程式需要有適當的SQL執行計劃，而這些新的執行計劃需要通過一些標準的測試獲得，使用SQL計劃基線能在隨時間的變化產生更好的效能
    DBMS_SPM包屬於SYS使用者，其他使用者需要被分配到ADMINISTER SQL MANAGEMENT OBJECT許可權才可以執行這個包
    ● CONFIGURE 程式
    這個程式用於設定SQL管理程式的配置選項，使用parameter/value 的格式。這個函式可能被呼叫多次，每次可以設定不同的值。
     

CONFIGURE Procedure

This procedure sets configuration options for SQL management base, in parameter/value format. This function can be called numerous times, each time setting a different configuration option.

Syntax

DBMS_SPM.CONFIGURE (    parameter_name    IN VARCHAR2,    parameter_value   IN NUMBER);

Parameters

Table 136-5 CONFIGURE Procedure Parameters

Parameter	Description
parameter_name	Name of parameter to set (see table below)
parameter_value	Value of parameter to use (see table below)

Table 136-6 Names & Values for CONFIGURE Procedure Parameters

Name	Description	Possible Values	Default Value
space_budget_percent	Maximum percent of SYSAUX space that can be used for SQL management base	1,2, …, 50	10
plan_retention_weeks	Number of weeks to retain unused plans before they are purged	5,6, …, 523	53

Usage Notes

• The default space budget for SQL management base is no more than ten percent of the size of SYSAUX tablespace. The space budget can be set to a maximum of 50%. The default unused plan retention period is one year and one week, which means a plan will be automatically purged if it has not been used for more than a year. The retention period can be set to a maximum of 523 weeks (i.e. a little over 10 years).

• When the space occupied by SQL management base exceeds the defined space budget limit, a weekly database alert is generated.

這個引數是設定最大的在SYSAUX空間上的百分比，並且如果超過空間閾值則每週會告警,所以選擇D

15.6.1 Disk Space Usage

Disk space used by the SMB is regularly checked against a limit based on the size of the SYSAUX tablespace. By default, the limit for the SMB is no more than 10% of the size of SYSAUX. The allowable range for this limit is between 1% and 50%.

A weekly background process measures the total space occupied by the SMB. When the defined limit is exceeded, the process writes a warning to the alert log. The database generates alerts weekly until one of the following conditions is met:

• The SMB space limit is increased

• The size of the SYSAUX tablespace is increased

• The disk space used by the SMB is decreased by purging SQL management objects (SQL plan baselines or SQL profiles)

To change the percentage limit, use the CONFIGURE procedure of the DBMS_SPM package. The following example changes the space limit to 30%:

BEGIN   DBMS_SPM.CONFIGURE('space_budget_percent',30); END; /