2017年Oracle OCP认证考试题库解析

　　Oracle公司颁布并实施的一项权威品的服务与支持。并具有娴熟的专业技术标准，它是专为认证那些有操作能力与广泛理论知识的专业人。下面是小编整理的Oracle OCP认证考试题库解析，欢迎大家参考!

　　QUESTION 1

　　You notice that the performance of the database has degraded because of frequent checkpoints.

　　Which two actions resolve the issue? (Choose two.)

　　A. Disable automatic checkpoint tuning

　　B. Check the size of the redo log file size and increase the size if it is small

　　C. Set the FAST_START_MTTR_TARGET parameter as per the advice given by the MTTR Advisor

　　D. Decrease the number of redo log members if there are more than one redo log members available in each redo log group

　　Correct Answer: BC

　　Explanation/Reference:

　　检查点进程:

　　The checkpoint process (CKPT) updates the control file and data file headers with checkpoint information and signals DBWn to write blocks to disk. Checkpoint information includes the checkpoint position, SCN, location in online redo log to begin recovery, and so on. CKPT does not write data blocks to data files or redo blocks to online redo log files.

　　检查点作用:

　　(1)定期促进DBWn进程把内存的脏块写回到数据文件,数据库故障时不会丢数据

　　(2)减少实例恢复的时间

　　(3)确保所有已提交的数据在一致性关闭期间会被写入数据文件

　　实例恢复时间:

　　指的是将数据文件的最后一个检查点(检查点位置)推进到控制文件中记录的最新SCN所需的时间.管理员可以通过设置MTTR 目标以及调整重做日志组的大小来控制该时间.

　　MTTR:

　　Mean Time To Repair,即平均修复时间.是指可修复产品的平均修复时间,就是从出现故障到修复中间的这段时间.MTTR越短表示易恢复性越好.在数据库中可以通过设置参数FAST_START_MTTR_TARGET(单位为秒),控制数据库对单个实例执行崩溃恢复所花费的时间.

　　FAST_START_MTTR_TARGE=非0值, 启用快速启动检查点功能,自动控制发检查点速度.

　　FAST_START_MTTR_TARGE=0,禁用快速启动检查点功能.

　　如果重做日志文件的size太小,会频繁切换日志,即会频繁发生检查点,故可以增大重做日志文件的size减少检查点发生频率.

　　FAST_START_MTTR_TARGET如果设置的太小,为了要控制数据库单实例的实例恢复时间，则必须频繁发生检查点,确保内存中已修改的数据块能够定期写入到磁盘,故可以使用MTTR Advisor来设置推荐的值.

　　QUESTION 2

　　Identify the memory component from which memory may be allocated for:Session memory for the shared server, Buffers for I/O slaves Oracle Database Recovery Manager (RMAN) backup and restore operations

　　A. Large Pool

　　B. Redo Log Buffer

　　C. Database Buffer Cache

　　D. Program Global Area (PGA)

　　Correct Answer: A

　　Explanation/Reference:

　　Large Pool

　　The large pool is an optional memory area intended for memory allocations that are larger than is appropriate for the shared pool. The large pool can provide large memory allocations for the following:

　　UGA for the shared server and the Oracle XA interface (used where transactions interact with multiple databases)

　　Message buffers used in the parallel execution of statements

　　Buffers for Recovery Manager (RMAN) I/O slaves

　　By allocating session memory from the large pool for shared SQL, the database avoids performance overhead caused by shrinking the shared SQL cache. By allocating memory in large buffers for RMAN operations, I/O server processes, and parallel buffers, the large pool can satisfy large memory requests better than the shared pool.

　　QUESTION 3

　　You executed the following command to create a tablespace called SALES_DATA:

　　SQL> CREATE TABLESPACE sales_data

　　DATAFILE SIZE 100M

　　SEGMENT SPACE MANAGEMENT AUTO;

　　Which two statements are true about the SALES_DATA tablespace? (Choose two)

　　A. The database automatically determines the extent-sizing policy for the tablespace.

　　B. The segments are automatically shrunk when the contents are removed from them.

　　C. The allocation of extents within the tablespace is managed through the dictionary tables.

　　D. The space utilization description of the data blocks in segments is recorded in bitmap blocks.

　　E. The space utilization description of the data blocks in segments is managed through free lists.

　　Correct Answer: AD

　　Explanation/Reference:

　　段空间管理: 本地管理的表空间中的段空间管理方式可指定为:

　　自动:Oracle DB 使用位图管理段中的空闲空间.位图描述了段中每个数据块的状态,该状态与可插入行的块中的空间量有关.当数据块中可用空间增多或减少时,位图中会反映数据块的新状态.通过使用位图,Oracle DB 可以提高管理空闲空间的自动化程度.因此,这种空间管理方式称为"自动段空间管理(ASSM)".

　　手动:此方法指定要使用空闲列表来管理段中的'空闲空间.空闲列表是由一些数据块组成的列表,这些数据块中有可插入行的空间.由于这种管理段空间的方式需要为在表空间中创建的方案对象指定并优化PCTUSED、FREELISTS和FREELIST GROUPS存储参数,因此这种方式称为"手动段空间管理".支持使用此方法是为了向后兼容,建议使用ASSM.

　　可通过dba_tablespaces查看分区和段空间管理方式:

　　SYS@ENMOEDU> select tablespace_name,extent_management,segment_space_management from dba_tablespaces;

　　TABLESPACE_NAME EXTENT_MAN SEGMEN

　　---------------- ---------- ------

　　SYSTEM LOCAL MANUAL

　　SYSAUX LOCAL AUTO

　　TEMP LOCAL MANUAL

　　USERS LOCAL AUTO

　　EXAMPLE LOCAL AUTO

　　UNDOTBS1 LOCAL MANUAL

　　QUESTION 4

　　In which of the scenario will the DBA perform recovery? (Choose all that apply.)