Oracle OCP 1Z0-050（41-50题）解析
QUESTION 41:
Exhibit #1:
Exhibit #2:
View the Exhibit exhibit1 to examine the series of SQL commands.
View the Exhibit exhibit2 to examine the plans available in the SQL plan baseline. The baseline in the first row of the Exhibit is created when OPTIMIZER_MODE was set to FIRST_ROWS.
Which statement is true if the SQL query in exhibit1 is executed again when the value of OPTIMIZER_MODE is set to FIRST_ROWS?
A. The optimizer uses the plan in the first row of the exhibit2 because OPTIMIZER_MODE was set to FIRST_ROW during its creation.
B. The optimizer uses the plan in the second row of the exhibit2 because it is an accepted plan.
C. The optimizer uses the plan in the first row of the exhibit2 because it is the latest generated plan.
D. The optimizer uses a new plan because none of the plans in the exhibit2 are fixed plans.
Answer: B
QUESTION 42:
What are the advantages of variable extent size support for large ASM files? (Choose two.)
A. It improves resync operations when the disk comes online after being taken offline for maintenance purposes.
B. It improves performance in the extended cluster configuration by reading from a local copy of an extent.
C. Fewer extent pointers are needed to describe the file and less memory is required to manage the extent maps in the shared pool.
D. This feature enables faster file opens because of the reduction in the amount of memory that is required to store file extents.
Answer: C,D
QUESTION 43:
Which two are the uses of the ASM metadata backup and restore (AMBR) feature?
(Choose two.)
A. It can be used to back up all data on ASM disks.
B. It can be used to recover the damaged ASM disk group along with the data.
C. It can be used to gather information about a preexisting ASM disk group with disk paths, disk name, failure groups, attributes, templates, and alias directory structure.
D. It can be used to re-create the ASM disk group with its attributes.
Answer: C,D
QUESTION 44:
Which two changes and their effect on the system can be tested by using the Database Replay feature? (Choose two.)
A. multiplexing of the control file
B. adding the redo log member to the database
C. database and operating system upgrades
D. changing the database storage to ASM-managed storage
Answer: C,D
QUESTION 45:
Which is the source used by Automatic SQL Tuning that runs as part of the AUTOTASK framework?
A. SQL statements that are part of the AWR baseline only
B. SQL statements based on the AWR top SQL identification
C. SQL statements that are part of the available SQL Tuning Set (STS) only
D. SQL statements that are available in the cursor cache and executed by a user other than SYS
Answer: B
QUESTION 46:
While performing the backup of the flash recovery area, you notice that one of the archived redo log files is missing. You have multiple destinations for archived redo log files. What implications does it have on the backup of the flash recovery area?
A. The backup fails because one of the archived redo log files is missing.
B. The backup succeeds but it would be without the missing archived log.
C. During backup, you are prompted for the alternative destination for the missing archived redo log file.
D. The backup succeeds because it fails over to one of the alternative archived redo log destinations.
Answer: D
QUESTION 47:
You are working on a CATDB database that contains an Oracle Database version 11.1 catalog schema owned by the user RCO11. The INST1 database contains an Oracle Database version 10.1 catalog schema owned by the user RCAT10.
You want the RMAN to import metadata for database IDs 1423241 and 1423242, registered in RCAT10, into the recovery catalog owned by RCO11. You executed the following commands:
RMAN> CONNECT CATALOG rco11/password@catdb
RMAN> IMPORT CATALOG rcat10/oracle@inst1 NO UNREGISTER;
Which two statements are true regarding the tasks accomplished with these commands?
(Choose two.)
A. They register all databases registered in the RCAT10 catalog.
B. They import all metadata from the RCAT10 catalog.
C. They do not register the databases registered in the RCAT10 catalog.
D. They unregister the database from the RCAT10 catalog.
Answer: A,B
解析：
使用IMPORT CATALOG命令可将元数据从一个恢复目录方案导入至其它目录方案中。如果创建了不同版本的目录方案来存储多个目标数据库的元数据，则使用此命令可以为所有数据库维护单个目录方案。
RMAN> CONNECT CATALOG rco11/password@catdb
1. RMAN 必须连接到需要将目录数据导入到的目标恢复目录，例如rco11 方案。
注：源恢复目录方案的版本必须等于RMAN 可执行文件的当前版本。导入早期版本的目录之前，必须将早期版本升级至RMAN 可执行文件的版本。
RMAN> IMPORT CATALOG rcat10/oracle@inst1;
2. 在本例中，ract10用户在inst1数据库中拥有一个RMAN 目录。你希望RMAN 导入所有注册的数据库并在源目录中注销这些数据库。
即是说，在RACT10目录中所有所注册的数据库到导入到rco11目录中，然后注销在ract10目录中所注册的数据库。
QUESTION 48:
You are managing an Oracle Database 11g instance and an Oracle Database 10g instance on the same machine. Both instances use the ASM instance as storage. Which statements regarding the ASM disk group compatibility attributes are true in this scenario? (Choose all that apply.)
A. The database-compatibility version settings for each instance must be greater than or equal to the RDBMS compatibility of all ASM disk groups used by that database instances.
B. RDBMS compatibility and the database version determines whether a database instance can mount the ASM disk group.
C. The RDBMS compatibility settings for a disk group control the format of data structures for ASM metadata on the disk.
D. ASM compatibility controls which features for the ASM will be enabled.
Answer: A,B,D
解析：
适用于ASM 磁盘组的兼容性有三种：涉及描述磁盘组的持久性数据结构，客户机（磁盘组的使用者）的功能，以及能否在磁盘组中包含卷。这些属性分别称为“ASM 兼容性”、“RDBMS 兼容性”和“ADVM 兼容性”。每个磁盘组的兼容性都可以独立控制。这是支持包含Oracle Database 10g和Oracle Database 11g磁盘组的异构环境所必需的。
这三种兼容性设置是每个ASM 磁盘组的属性：
• RDBMS 兼容性是指RDBMS 实例的最低兼容版本，此设置将允许该实例装载磁盘组。
该兼容性确定了ASM 实例与数据库(RDBMS) 实例间交换消息的格式。ASM 实例可以支持以不同兼容性设置运行的不同RDBMS 客户机。每个实例的数据库兼容版本设置必须高于或等于该数据库使用的所有磁盘组的RDBMS 兼容性。数据库实例与ASM 实例通常在不同的Oracle 主目录中运行。这意味着数据库实例可以运行与ASM 实例不同的软件版本。数据库实例第一次连接到ASM实例时，系统会协定这两个实例都支持的最高版本。
数据库的兼容性参数设置、数据库的软件版本以及磁盘组的RDBMS 兼容性设置确定了数据库实例能否装载给定的磁盘组。
• ASM 兼容性是指控制磁盘上ASM 元数据的数据结构格式的持久性兼容性设置。
磁盘组的ASM 兼容性级别必须始终高于或等于同一磁盘组的RDBMS 兼容性级别。
ASM 兼容性只与ASM 元数据的格式相关。文件内容的格式取决于数据库实例。例如，可以将某个磁盘组的ASM 兼容性设置为11.0，而将该磁盘组的RDBMS 兼容性设置为10.1。这意味着该磁盘组只能由软件版本为11.0 或更高的ASM 软件管理，而软件版本高于或等于10.1 的任何数据库客户机都可以使用该磁盘组。
• ADVM 兼容性属性确定磁盘组能否包含Oracle ASM 卷。该值必须设置为11.2 或更高。设置该属性前，必须确保COMPATIBLE.ASM的值为11.2 或更高。此外，还必须加载ADVM 卷驱动程序。
仅当持久性磁盘结构或消息传送协议发生更改时，才需要提高磁盘组的兼容性。但是，提高磁盘组兼容性是一个不可逆的操作。可以使用CREATE DISKGROUP命令或ALTER DISKGROUP命令来设置磁盘组兼容性。
注：除了磁盘组兼容性，兼容参数（数据库兼容版本）确定了启用的功能；该参数适用于数据库或ASM 实例，具体取决于instance_type参数。例如，将该参数设置为10.1 将禁止使用Oracle Database 11g中引入的任何新功能（磁盘联机/脱机、可变区等）。
QUESTION 49:
Which two statements about Oracle Direct Network File System (NFS) are true? (Choose two.)
A. It uses the operating system kernel NFS layer for user tasks and network communication modules.
B. File systems need not be mounted by the kernel NFS system when being served through Direct NFS.
C. Oracle Disk Manager can manage NFS on its own, without using the operating system kernel NFS driver.
D. A separate NFS interface is required for use across Linux, UNIX, and Windows platforms.
E. It bypasses the OS file system cache.
Answer: C,E
解析：
参考Oracle官方文档：
https://docs.oracle.com/cd/E11882_01/install.112/e41962/whatsnew.htm#RILIN954
Oracle Disk Manager Network File System Management
Oracle Disk Manager (ODM) can manage network file systems (NFS) on its own, without using the operating system kernel NFS driver. This is referred to as Direct NFS. Direct NFS implements NFS version 3 protocol within the Oracle Database kernel. This change enables monitoring of NFS status using the ODM interface. The Oracle Database kernel driver tunes itself to obtain optimal use of available resources.
This feature provides the following:
Ease of tuning, and diagnosability, by providing the Oracle kernel control over the input-output paths to Network File Server, and avoiding the need to tune network performance at the operating system level.
A highly stable, highly optimized NFS client for database operations.
Use of the Oracle network file system layer for user tasks, reserving the operating system kernel network file system layer for network communication.
Use of the Oracle buffer cache, rather than the file system cache, for simpler tuning.
A common, consistent NFS interface, capable for use across Linux, UNIX and Windows platforms.
Oracle RAC aware NFS performance. With operating system NFS drivers, even though NFS is a shared file system, NFS drives have to be mounted with the option noac (NO Attribute Caching) to prevent the operating system NFS driver from optimizing the filesystem cache by storing file attributes locally. ODM NFS automatically recognizes Oracle RAC instances, and performs appropriate operations for datafiles without requiring additional reconfiguration from users, system administrators, or DBAs. If you store the Oracle Clusterware voting disks or Oracle Cluster Registry (OCR) files on NFS, then you must continue to require mounting voting disks with the noac option.
QUESTION 50:
Which three statements are true regarding the functioning of the Autotask Background Process (ABP)? (Choose three.)
A. It creates jobs without considering the priorities associated with them.
B. It translates tasks into jobs for execution by the scheduler.
C. It determines the list of jobs that must be created for each maintenance window.
D. It is spawned by the MMON background process at the start of the maintenance window.
E. It maintains a repository in the SYSTEM tablespace to store the history of the execution of all tasks.
Answer: B,C,D
解释：
ABP相当于自动任务与调度程序之间的中介，其主要作用是将自动任务转换成Autotask作业，供调度程序执行。同样重要的是，ABP还维护所有任务执行的历史记录。ABP将其专用资料档案库存储在sysaux表空间中，您可以通过DBA_AUTOTASK_TASK 查案该资料档案库。
ABP是在启动维护窗口时，由MMON 启动的，所有实例只需要一个ABP。MMON进程将监视ABP，并在必要时重启ABP.
ABP可以确定为每项维护任务创建的作业列表，此列表按以下优先级排序：紧急、高级、中级。在每个优先级组中，作业是按执行的首选顺序排列的。
ABP按照以下方式创建作业：先创建所有紧急优先级的作业，然后创建高优先级的作业，最后创建所有中优先级的作业。
ABP将作业分配到多个调度程序作业类。这些作业类将作业映射到基于优先级的使用者组。
注意：使用Oracle DB 11g时，不存在与特定任务永久关联的作业。因此，不能使用DBMS_SCHEDULER过程来控制自动任务的行为，请改而使用DBMS_AUTO_TASK_ADMIN过程