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2017年Oracle OCP認(rèn)證考試題庫解析
Oracle公司頒布并實(shí)施的一項(xiàng)權(quán)威品的服務(wù)與支持。并具有嫻熟的專業(yè)技術(shù)標(biāo)準(zhǔn)，它是專為認(rèn)證那些有操作能力與廣泛理論知識(shí)的專業(yè)人。下面是小編整理的Oracle OCP認(rèn)證考試題庫解析，歡迎大家參考!
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:
檢查點(diǎn)進(jìn)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(diǎn)作用:
(1)定期促進(jìn)DBWn進(jìn)程把內(nèi)存的臟塊寫回到數(shù)據(jù)文件,數(shù)據(jù)庫故障時(shí)不會(huì)丟數(shù)據(jù)
(2)減少實(shí)例恢復(fù)的時(shí)間
(3)確保所有已提交的數(shù)據(jù)在一致性關(guān)閉期間會(huì)被寫入數(shù)據(jù)文件
實(shí)例恢復(fù)時(shí)間:
指的是將數(shù)據(jù)文件的最后一個(gè)檢查點(diǎn)(檢查點(diǎn)位置)推進(jìn)到控制文件中記錄的最新SCN所需的時(shí)間.管理員可以通過設(shè)置MTTR 目標(biāo)以及調(diào)整重做日志組的大小來控制該時(shí)間.
MTTR:
Mean Time To Repair,即平均修復(fù)時(shí)間.是指可修復(fù)產(chǎn)品的平均修復(fù)時(shí)間,就是從出現(xiàn)故障到修復(fù)中間的這段時(shí)間.MTTR越短表示易恢復(fù)性越好.在數(shù)據(jù)庫中可以通過設(shè)置參數(shù)FAST_START_MTTR_TARGET(單位為秒),控制數(shù)據(jù)庫對(duì)單個(gè)實(shí)例執(zhí)行崩潰恢復(fù)所花費(fèi)的時(shí)間.
FAST_START_MTTR_TARGE=非0值, 啟用快速啟動(dòng)檢查點(diǎn)功能,自動(dòng)控制發(fā)檢查點(diǎn)速度.
FAST_START_MTTR_TARGE=0,禁用快速啟動(dòng)檢查點(diǎn)功能.
如果重做日志文件的size太小,會(huì)頻繁切換日志,即會(huì)頻繁發(fā)生檢查點(diǎn),故可以增大重做日志文件的size減少檢查點(diǎn)發(fā)生頻率.
FAST_START_MTTR_TARGET如果設(shè)置的太小,為了要控制數(shù)據(jù)庫單實(shí)例的實(shí)例恢復(fù)時(shí)間，則必須頻繁發(fā)生檢查點(diǎn),確保內(nèi)存中已修改的數(shù)據(jù)塊能夠定期寫入到磁盤,故可以使用MTTR Advisor來設(shè)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為:
自動(dòng):Oracle DB 使用位圖管理段中的空閑空間.位圖描述了段中每個(gè)數(shù)據(jù)塊的狀態(tài),該狀態(tài)與可插入行的塊中的空間量有關(guān).當(dāng)數(shù)據(jù)塊中可用空間增多或減少時(shí),位圖中會(huì)反映數(shù)據(jù)塊的新狀態(tài).通過使用位圖,Oracle DB 可以提高管理空閑空間的自動(dòng)化程度.因此,這種空間管理方式稱為"自動(dòng)段空間管理(ASSM)".
手動(dòng):此方法指定要使用空閑列表來管理段中的空閑空間.空閑列表是由一些數(shù)據(jù)塊組成的列表,這些數(shù)據(jù)塊中有可插入行的空間.由于這種管理段空間的方式需要為在表空間中創(chuàng)建的方案對(duì)象指定并優(yōu)化PCTUSED、FREELISTS和FREELIST GROUPS存儲(chǔ)參數(shù),因此這種方式稱為"手動(dòng)段空間管理".支持使用此方法是為了向后兼容,建議使用ASSM.
可通過dba_tablespaces查看分區(qū)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(shù)據(jù)庫出現(xiàn)介質(zhì)損壞的時(shí)候執(zhí)行恢復(fù)操作.
A: 錯(cuò)誤,alert日志損壞數(shù)據(jù)庫不會(huì)丟失數(shù)據(jù),不需要恢復(fù).
B: 正確,表空間在操作系統(tǒng)改名需要執(zhí)行恢復(fù),數(shù)據(jù)庫找不到表空間對(duì)應(yīng)的數(shù)據(jù)文件.
C: 錯(cuò)誤,丟失redo成員,不會(huì)丟失數(shù)據(jù),不需要執(zhí)行恢復(fù)操作.
D: 錯(cuò)誤,會(huì)話異常終止不會(huì)丟失數(shù)據(jù),不需要恢復(fù),數(shù)據(jù)庫會(huì)釋放異常會(huì)話占用的資源.
E: 正確,磁盤損壞會(huì)導(dǎo)致在該磁盤的數(shù)據(jù)文件損壞,需要執(zhí)行恢復(fù)操作.
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