Oracle開發的關係數據庫產品因性能卓越而聞名，Oracle數據庫產品爲財富排行榜上的前1000家公司所採用，許多大型網站也選用了Oracle系統，是世界最好的數據庫產品。以下是小編整理的關於Oracle OCP認證考試題庫，希望大家認真閱讀!
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:
檢查點進程:
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.
檢查點作用:
(1)定期促進DBWn進程把內存的髒塊寫回到數據文件,數據庫故障時不會丟數據
(2)減少實例恢復的時間
(3)確保所有已提交的數據在一致性關閉期間會被寫入數據文件
實例恢復時間:
指的是將數據文件的最後一個檢查點(檢查點位置)推進到控制文件中記錄的最新SCN所需的時間.管理員可以通過設置MTTR 目標以及調整重做日誌組的大小來控制該時間.
MTTR:
Mean Time To Repair,即平均修復時間.是指可修復產品的平均修復時間,就是從出現故障到修復中間的`這段時間越短表示易恢復性越好.在數據庫中可以通過設置參數FAST_START_MTTR_TARGET(單位爲秒),控制數據庫對單個實例執行崩潰恢復所花費的時間.
FAST_START_MTTR_TARGE=非0值, 啓用快速啓動檢查點功能,自動控制發檢查點速度.
FAST_START_MTTR_TARGE=0,禁用快速啓動檢查點功能.
如果重做日誌文件的size太小,會頻繁切換日誌,即會頻繁發生檢查點,故可以增大重做日誌文件的size減少檢查點發生頻率.
FAST_START_MTTR_TARGET如果設置的太小,爲了要控制數據庫單實例的實例恢復時間，則必須頻繁發生檢查點,確保內存中已修改的數據塊能夠定期寫入到磁盤,故可以使用MTTR Advisor來設置推薦的值.
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:
段空間管理: 本地管理的表空間中的段空間管理方式可指定爲:
自動:Oracle DB 使用位圖管理段中的空閒空間.位圖描述了段中每個數據塊的狀態,該狀態與可插入行的塊中的空間量有關.當數據塊中可用空間增多或減少時,位圖中會反映數據塊的新狀態.通過使用位圖,Oracle DB 可以提高管理空閒空間的自動化程度.因此,這種空間管理方式稱爲"自動段空間管理(ASSM)".
手動:此方法指定要使用空閒列表來管理段中的空閒空間.空閒列表是由一些數據塊組成的列表,這些數據塊中有可插入行的空間.由於這種管理段空間的方式需要爲在表空間中創建的方案對象指定並優化PCTUSED、FREELISTS和FREELIST GROUPS存儲參數,因此這種方式稱爲"手動段空間管理".支持使用此方法是爲了向後兼容,建議使用ASSM.
可通過dba_tablespaces查看分區和段空間管理方式:
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.)
A. The alert log file is corrupted
B. A tablespace is accidentally dropped
C. One of the redo log members is corrupted
D. A database user terminates the session abnormally
E. The hard disk on which the data files is stored is corrupted
Correct Answer: BE
Explanation/Reference:
DBA一般在數據庫出現介質損壞的時候執行恢復操作.
A: 錯誤,alert日誌損壞數據庫不會丟失數據,不需要恢復.
B: 正確,表空間在操作系統改名需要執行恢復,數據庫找不到表空間對應的數據文件.
C: 錯誤,丟失redo成員,不會丟失數據,不需要執行恢復操作.
D: 錯誤,會話異常終止不會丟失數據,不需要恢復,數據庫會釋放異常會話佔用的資源.
E: 正確,磁盤損壞會導致在該磁盤的數據文件損壞,需要執行恢復操作.
