1Z0-050

标签：

QUESTION 13

View the Exhibit.

Examine the following command that is executed for the TRANSPORT table in the SH schema:
SQL> SELECT DBMS_STATS.CREATE_EXTENDED_STATS(‘sh‘, ‘customers_obe‘, ‘(country_id,
cust_state_province)‘) FROM dual;
Which statement describes the significance of this command?

• A. It collects statistics into the pending area in the data dictionary.
• B. It creates a virtual hidden column in the CUSTOMERS_OBE table.
• C. It collects statistics with AUTO_SAMPLE_SIZE for ESTIMATE_PERCENT.
• D. It creates a histogram to hold skewed information about the data in the columns.

Answer: B

创建一个虚拟隐含列
对于where条件里具有两个列以上的情况，比如where c1=’A’ and c2=’B’来说，11g以前优化器评估其selectivity时，总是将每个列的selectivity相乘，从而得到整个where条件的selectiviey。但是如果两个列具有很强的依赖关系，比如汽车制造商与汽车型号这两个列来说，我们知道每个汽车制造商所生产的汽车型号几乎都不会重复，也就是说当你发出where 汽车制造商列=’XXX’ and 汽车型号列=’XXX’时，与发出where汽车型号列=’XXX’时返回的记录行数可能几乎一样。这时如果在计算where条件的selectivity时仍然采用将汽车制造商列的selectivity乘以汽车型号列的selectivity时，就会导致总的selectivity过低，从而导致优化器估计返回的记录行数过少，从而可能导致不正确的执行计划。
为了弥补这样的问题，11g以后可以让你将多个依赖程度很高列合并成一个组，然后对该组收集统计信息。具体如何实现，则可以看下面的例子。

select dbms_stats.create_extended_stats（‘Schema_name‘,‘Table_name‘,‘（C1,C2）‘） from dual;

通过调用函数dbms_stats.create_extended_stats将两个或多个列合并，并返回一个虚拟的隐藏列的列名，其名字类似于：SYS_STUW_5RHLX443AN1ZCLPE_GLE4。
然后，我们可以开始对表收集统计信息，收集完以后，你可以使用ALL|DBA|USER_STAT_EXTIONSIONS视图来查看列组合的统计信息。

exec dbms_stats.gather_table_stats（‘Schema_name‘,‘Table_name‘）；

如果你要对组合列收集直方图，则可以如下所示：

exec dbms_stats.gather_table_stats（‘Schema_name‘,‘Table_name‘,
method_opt=>‘for columns （C1,C2） size AUTO‘）；

参考：050解析

QUESTION 14

View the Exhibit to examine the parameter values.

You are planning to set the value for the MEMORY_TARGET parameter of your database instance.
What value would you assign?
A. 90 MB
B. 272 MB
C. 362 MB
D. 1440 MB
Answer: C
没什么好说的，Memory=SGA+PGA

QUESTION 15

You installed Oracle Database 11g and are performing a manual upgrade of the Oracle9i database. As a
part of the upgrade process, you execute the following script:
SQL>@utlu111i.sql.
Which statement about the execution of this script is true?
A. It must be executed from the Oracle Database 11g environment.
B. It must be executed only after the SYSAUX tablespace has been created.
C. It must be executed from the environment of the database that is being upgraded.
D. It must be executed only after AUTOEXTEND is set to ON for all existing tablespaces.
E. It must be executed from both the Oracle Database 11g and Oracle Database 9i environments.
Answer: C

在被升级的库中执行Analyze the existing instance
Upgrading to Oracle Database 11g
http://www.oracleflash.com/38/Oracle-11g-Release-1-Pre-Upgrade-tool-utlu111i-sql.html#databasesection

QUESTION 16

Which three statements about performance analysis by SQL Performance Analyzer are true? (Choose
three.)
A. It detects changes in SQL execution plans.
B. It produces results that can be used to create the SQL plan baseline.
C. The importance of SQL statements is based on the size of the objects accessed.
D. It generates recommendations to run SQL Tuning Advisor to tune regressed SQLs.
E. It shows only the overall impact on workload and not the net SQL impact on workload.
Answer: ABD

http://docs.oracle.com/cd/E11882_01/server.112/e41481/spa_intro.htm#RATUG166

QUESTION 17

Which tasks can be accomplished using the Enterprise Manager Support Workbench in Oracle Database
11g? (Choose all that apply.)
A. Generate reports on data failure such as data file failures.
B. You can package and upload diagnostic data to Oracle Support.
C. You can track the Service Request (SR) and implement repairs.
D. You can manually run health checks to gather diagnostic data for a problem.
Answer: BCD

QUESTION 18

Which statement is true regarding the VALIDATE DATABASE command?
A. It checks the database for intrablock corruptions only.
B. It checks for block corruption in the valid backups of the database.
C. It checks the database for both intrablock and interblock corruptions.
D. It checks for only those corrupted blocks that are associated with data files.
Answer: A

QUESTION 19

Which two are the prerequisites to enable Flashback Data Archive? (Choose two.)
A. Undo retention guarantee must be enabled.
B. Database must be running in archivelog mode.
C. Automatic undo management must be enabled.
D. The tablespace on which the Flashback Data Archive is created must be managed with Automatic
Segment Space Management (ASSM).
Answer: CD

QUESTION 20

You are managing the APPPROD database as a DBA. You plan to duplicate this database in the same
system with the name DUPDB.
You issued the following RMAN commands to create a duplicate database:

RMAN> CONNECT target sys/sys@APPPROD
RMAN> DUPLICATE TARGET DATABASE
TO dupdb
FROM ACTIVE DATABASE
DB_FILE_NAME_CONVERT ‘/oracle/oradata/prod/‘,
‘/scratch/oracle/oradata/dupdb/‘
SPILE
PARAMETER_VALUE_CONVERT ‘/oracle/oradata/prod/‘,
‘/scratch/oracle/oradata/dupdb/‘
SET SGA_MAX_SIZE = ‘300M‘
SET SGA_TARGET = ‘250M‘
SET LOG_FILE_NAME_CONVERT ‘/oracle/oradata/prod/redo/‘, ‘/scratch/oracle/oradata/dupdb/redo/‘;

Which three are the prerequisites for the successful execution of the above command? (Choose three.)

A. The source database should be open.
B. The target database should be in ARCHIVELOG mode if it is open.
C. RMAN should be connected to both the instances as SYSDBA.
D. The target database backups should be copied to the source database backup directories.
E. The password file must exist for the source database and have the same SYS user password as the
target.

Answer: BCE

A,源数据库应该为打开，错误，也可以是mount状态。
D,目标数据库的备份必须拷贝到源数据库目录。错误，上面的复制数据库语句是从活动的数据库来复制的，不需要备份。

Prerequisites Specific to Active Database Duplication

When you execute DUPLICATE with FROM ACTIVE DATABASE, at least one normal target channel and at least one AUXILIARY channel are required.
When you connect RMAN to the source database as TARGET, you must specify a password, even if RMAN uses operating system authentication. The source database must be mounted or open. If the source database is open, then archiving must be enabled. If the source database is not open, then it must have been shut down consistently.

When you connect RMAN to the auxiliary instance, you must provide a net service name. This requirement applies even if the auxiliary instance is on the local host.

The source database and auxiliary instances must use the same SYSDBA password, which means that both instances must have password files. You can create the password file with a single password so you can start the auxiliary instance and enable the source database to connect to it.

The DUPLICATE behavior for password files varies depending on whether your duplicate database acts as a standby database. If you create a duplicate database that is not a standby database, then RMAN does not copy the password file by default. You can specify the PASSWORD FILE option to indicate that RMAN should overwrite the existing password file on the auxiliary instance. If you create a standby database, then RMAN copies the password file to the standby host by default, overwriting the existing password file. In this case, the PASSWORD FILE clause is not necessary.

You cannot use the UNTIL clause when performing active database duplication. RMAN chooses a time based on when the online data files have been completely copied, so that the data files can be recovered to a consistent point in time.

1Z0-050

标签：

原文地址：http://www.cnblogs.com/haoxiaoyu/p/c893e687d9d866fc1667e66875c91ffc.html