Oracle 11gOCP 053 v12.02 1--300题疑问答案更正

5 - Health Monitor

Examine the section ofthe Health Check report given below:
DBMS_HM.GET_RUN_REPORT('HM_RUN_1061')
Run Name : HM_RUN_1061Run Id : 1061
Check Name : DataBlock Integrity
Check Mode : REACTIVE
Status : COMPLETED
Start Time :2007-05-12 22:11:02.032292 -07:00
End Time : 2007-05-1222:11:20.835135 -07:00
Error Encountered : 0
Source Incident Id :7418
Number of IncidentsCreated :0
Which two statementsare true regarding the Health Check report? (Choose two.)
A. HealthCheck was performed manually.
B. Health Check wasperformed to check the disk
imageblock corruptions.
C. Health Check wasperformed to check
interblock and intersegmentcorruption.
D. Health Check wasperformed to verify the
integrityof database filesand report failures.
E. Health Check wasperformed by the Health Monitor
automatically inresponse to a critical error.
解析:

同类型140题

http://docs.oracle.com/cd/E11882_01/server.112/e25494/diag.htm#ADMIN11271

AboutHealth Monitor Checks

Health Monitor checks (also known as checkers, health checks, orchecks) examine various layers and components of the database. Health checksdetect file corruptions, physical
and logical block corruptions, undo and redocorruptions, data dictionary corruptions, and more. The health checks generatereports of their findings and, in many cases, recommendations for resolvingproblems. Health checks can be run in two ways:

·        Reactive—The fault diagnosability infrastructure can run health checksautomatically in response
to a critical error.

·        Manual—As a DBA, you can manually run health checks using either the 

DBMS_HM

 PL/SQLpackage
or the Enterprise Manager interface. You can run checkers on a regularbasis if desired, or Oracle Support may ask you to run a checker while workingwith you on a service request.

HealthMonitor checks store findings, recommendations, and other information in theAutomatic Diagnostic Repository (ADR).

Healthchecks can run in two modes:

·        DB-online mode means the check can be run while the database is open (thatis, in 

OPEN

 mode
or 

MOUNT

 mode).

·        DB-offline mode means the check can be run when the instance is availablebut the database itself
is closed (that is, in 

NOMOUNT

 mode).

All thehealth checks can be run in DB-online mode. Only the Redo Integrity Check andthe DB Structure Integrity Check can be used in DB-offline mode.

http://docs.oracle.com/cd/E11882_01/server.112/e25494/diag.htm#ADMIN11274

Typesof Health Checks

Healthmonitor runs the following checks:

·        DB Structure IntegrityCheck—This checkverifies the integrity of database files and reports failures if these filesare inaccessible,
corrupt or inconsistent. If the database is in mount or openmode, this check examines the log files and data files listed in the controlfile. If the database is in 

NOMOUNT

 mode,
only the control file is checked.

·        Data Block IntegrityCheck—This checkdetects disk image block corruptions such as checksum failures,
head/tailmismatch, and logical inconsistencies within the block. Most corruptions can be repaired using Block Media Recovery.Corrupted block information is also captured in the

V$DATABASE_BLOCK_CORRUPTION

 view.
This check does not detect inter-block or inter-segmentcorruption.

·        Redo Integrity Check—This check scans the contents of the redo log for accessibilityand corruption, as well as the archive logs, if
available. The Redo IntegrityCheck reports failures such as archive log or redo corruption.

·        Undo Segment IntegrityCheck—This checkfinds logical undo corruptions. After locating an undo corruption, this checkuses PMON and SMON
to try to recover the corrupted transaction. If thisrecovery fails, then Health Monitor stores information about the corruption in 

V$CORRUPT_XID_LIST

. Most undo corruptions
can be resolved by forcing a commit.

·        Transaction IntegrityCheck—This checkis identical to the Undo Segment Integrity Check except that it checks only onespecific transaction.

·        Dictionary IntegrityCheck—This checkexamines the integrity of core dictionary objects, such as 

tab$

 and 

col$

.
Itperforms the following operations:

o    Ve
4000
rifies thecontents of dictionary entries for each dictionary object.

o    Performs across-row level check, which verifies that logical constraints on rows in thedictionary are enforced.

o    Performs anobject relationship check, which verifies that parent-child relationships betweendictionary objects are enforced.

The Dictionary Integrity Check operates on the followingdictionary objects:

tab$

, 

clu$

, 

fet$

, 

uet$

, 

seg$

, 

undo$

, 

ts$

, 

file$

, 

obj$

, 

ind$

, 

icol$

, 

col$

, 

user$

, 

con$

, 

cdef$

, 

ccol$

, 

bootstrap$

, 

objauth$

, 

ugroup$

, 

tsq$

, 

syn$

, 

view$

,

typed_view$

, 

superobj$

, 

seq$

, 

lob$

, 

coltype$

, 

subcoltype$

, 

ntab$

, 

refcon$

, 

opqtype$

, 

dependency$

, 

access$

, 

viewcon$

, 

icoldep$

, 

dual$

, 

sysauth$

,

objpriv$

, 

defrole$

,
and 

ecol$

.

 

http://docs.oracle.com/cd/E11882_01/server.112/e25494/diag.htm#ADMIN11274
RunningHealth Checks Using the DBMS_HM PL/SQL Package

The 

DBMS_HM

 procedurefor running a health check is called 

RUN_CHECK

.
To call 

RUN_CHECK

, supply the name of the check and a name for the run, asfollows:

BEGIN

  DBMS_HM.RUN_CHECK('Dictionary Integrity Check', 'my_run');

END;

/

To obtain alist of health check names, run the following query:

SELECT name FROM v$hm_check WHERE internal_check='N';

NAME

----------------------------------------------------------------

DB Structure Integrity Check

Data Block Integrity Check

Redo Integrity Check

Transaction Integrity Check

Undo Segment Integrity Check

Dictionary Integrity Check

Most healthchecks accept input parameters. You can view parameter names and descriptionswith the 

V$HM_CHECK_PARAM

 view.
Some parameters are mandatory while others are optional.If optional parameters are omitted, defaults are used. The following querydisplays parameter information for all health checks:

SELECT c.name check_name, p.name parameter_name, p.type,

p.default_value, p.description

FROM v$hm_check_param p, v$hm_check c

WHERE p.check_id = c.id and c.internal_check = 'N'

ORDER BY c.name;

Inputparameters are passed in the 

input_params

 argument as name/value pairs separated by semicolons (;). Thefollowing
example illustrates how to pass the transaction ID as a parameter tothe Transaction Integrity Check:

BEGIN

  DBMS_HM.RUN_CHECK (

   check_name   => 'Transaction Integrity Check',

   run_name     => 'my_run',

   input_params => 'TXN_ID=7.33.2');

END;

/

Answer:BE

24 - SQL Test Case Builder

Which of the following information will be gathered by the
SQL Test Case Builder for the problems pertaining toSQL-related problems? (Choose all that apply.)
A. ADR diagnostic files
B. all the optimizer statistics
C. initialization parameter settings
D. PL/SQL functions, procedures, and packages
E. the table and index definitions and actual data
 
解析:

For manySQL-related problems, obtaining a reproducible test case makes it easier toresolve the problem. Starting with the 11g Release 1 (11.1), Oracledatabase contains the SQL
Test Case Builder, whichautomates the somewhat difficult and time-consuming process of gathering andreproducing as much information as possible about a problem and the environmentin which it occurred.
The objective ofa SQL Test Case Builder is to capturethe information pertaining to aSQL-related problem, along with the exact environment under which the problemoccurred, so that the problem can be reproduced
and tested on a separateOracle database instance. Once the test case is ready, you can upload theproblem to Oracle Support to enable support personnel to reproduce andtroubleshoot the problem.
The informationgathered by SQL Test Case Builder includes the
query beingexecuted,
table and indexdefinitions (but not the actual data),
PL/SQL functions,procedures, and packages,
optimizer statistics,and initialization parameter settings.
http://docs.oracle.com/cd/B28359_01/server.111/b28274/sql_overview.htm#PFGRF16001
Building SQL Test Cases

http://docs.oracle.com/cd/B28359_01/server.111/b28274/sql_overview.htm#PFGRF16001
Answer: BCD

46 - SQLTuning Advisor

What happens when you run the
SQL Tuning Advisor withlimited scope?
A. Access path analysis is not performed for SQL statements.
B. SQL structureanalysis
is notperformed for SQL statements.
C. SQL Profile recommendations are not generatedfor SQL statements.
D. Staleness and absence of statistics are not checked for theobjects in the SQL Tuning Advisor.
 
解析:

同类型 253、298题

http://docs.oracle.com/cd/E11882_01/server.112/e41573/sql_tune.htm#PFGRF94853

Tuning Options

SQL Tuning Advisorprovides options to manage the scope and duration of a tuning task. You can setthe scope of a tuning task either of the following:

·        Limited

In thiscase, SQL Tuning Advisor produces recommendations based on statistical checks,access path analysis, and SQL structure analysis.SQL profile recommendationsare not generated.

·        Comprehensive

In thiscase, SQL Tuning Advisor carries out all the analysis it performs under limitedscope plus SQL Profiling. With the comprehensive option you can also specify atime limit for the tuning task, which by default is 30 minutes.

 

http://docs.oracle.com/cd/E11882_01/server.112/e10897/montune.htm#ADMQS1037

About theAutomatic SQL Tuning Advisor

Beginning with OracleDatabase 11g, the SQL Tuning Advisor runsautomatically during system maintenance windows (time periods) as a maintenancetask. During
each automatic run, the advisor selects high-load SQL queries inthe system and generates recommendations on how to tune these queries.

The Automatic SQL TuningAdvisor can be configured to automatically implement SQL profilerecommendations.

A SQLprofile containsadditional SQL statistics that are specific to the SQL statement and enable thequery optimizer to generate a significantly better execution plan at run time.

If you enable automatic implementation, then the advisor createsSQL profiles for only those SQL statements where the performance increase wouldbe at least threefold. Other types of recommendations, such as the creation ofnew indexes,
refreshing optimizer statistics, or restructuring SQL, can beimplemented only manually.DML statementsare not considered for tuning by the Automatic SQL Tuning Advisor.

You can view a summary of the results of automatic SQL tuningover a specified period (such as the previous 7 days), and a detailed reportabout recommendations made for all SQL statements that the SQL Tuning Advisorhas processed.
You can then implement selected recommendations. You can alsoview the recommendations that were automatically implemented.

You can control when the Automatic SQL Tuning Advisor runs, andyou can disable it if desired.

 

SQL Tuning Advisor

The SQL Tuning Advisor takesone or more SQL statements as an input and invokes the Automatic TuningOptimizer
to perform SQL tuning on the statements. The output of the SQL TuningAdvisor is in the form of an advice or recommendations, along with arationale for each r
14e66
ecommendation and its expected benefit.

The recommendationrelates to collection of statistics on objects, creation of new indexes,restructuring of the SQL statement, or creation of a SQL profile. You
canchoose to accept the recommendation to complete the tuning of the SQLstatements.

Oracle Database canautomatically tune SQL statements by identifying problematic SQL statements andimplementing tuning recommendations using the SQL Tuning Advisor during systemmaintenance windows. You can also run the SQL Tuning
Advisor selectively on asingle or a set of SQL statements that have been identified as problematic.

http://docs.oracle.com/cd/B28359_01/server.111/b28274/sql_tune.htm#CHDJDFGE

Automatic SQL Tuning

Automatic SQLtuning runs as part of the automated maintenance tasks infrastructure.
To enableautomatic SQL tuning, use the ENABLE procedure in the DBMS_AUTO_TASK_ADMIN package:
BEGIN
  DBMS_AUTO_TASK_ADMIN.ENABLE(
    client_name => 'sql tuning advisor',
    operation => NULL,
    window_name => NULL);
END;
/
To disableautomatic SQL tuning, use the DISABLE procedure in the DBMS_AUTO_TASK_ADMINpackage:
BEGIN
  DBMS_AUTO_TASK_ADMIN.DISABLE(
    client_name => 'sql tuning advisor',
    operation => NULL,
    window_name => NULL);
END;
Running SQL TuningAdvisor using 

DBMS_SQLTUNE

 package is a multi-step process:

1.   Create a SQL Tuning Set (if tuning multiple SQL statements)

2.   Create a SQL tuning task

3.   Execute a SQL tuning task

4.   Display the results of a SQL tuning task

5.   Implement recommendations as appropriate

 SQL Tuning Advisor APIs

http://docs.oracle.com/cd/B28359_01/server.111/b28274/sql_tune.htm#CHDIHFHA

Answer:C

66 - Parameter STATISTICS_LEVEL

Which two initialization parameters would you set to enableAutomatic Shared Memory Management?
(Choose two.)
A. set SHARED_POOL_SIZE to zero
B. set STATISTICS_LEVEL to BASIC
C. set SGA_TARGET to a non-zero value
D. set DB_CACHE_SIZE to a non-zero value
E. set STATISTICS_LEVEL to TYPICALor ALL
解析:

http://docs.oracle.com/cd/E11882_01/server.112/e40402/initparams254.htm#REFRN10214

STATISTICS_LEVEL

Property	Description
Parameter type	String
Syntax	STATISTICS_LEVEL = { ALL | TYPICAL | BASIC }
Default value	TYPICAL
Modifiable	ALTER SESSION ,  ALTER SYSTEM

 

STATISTICS_LEVEL

 specifies the level of collection for database and operatingsystem statistics. The Oracle Database collects these statistics for
a varietyof purposes, including making self-management decisions.

The default setting of 

TYPICAL

 ensures collection of all major statistics required for databaseself-management
functionality and provides best overall performance. Thedefault value should be adequate for most environments.

When the 

STATISTICS_LEVEL

 parameter is set to 

ALL

,
additionalstatistics are added to the set of statistics collected with the 

TYPICAL

 setting. The additional statistics are timed OS statistics
andplan execution statistics.

Setting the 

STATISTICS_LEVEL

 parameter to 

BASIC

 disables
the collection of many of the important statisticsrequired by Oracle Database features and functionality, including:

·        Automatic Workload Repository (AWR) Snapshots

·        Automatic Database Diagnostic Monitor (ADDM)

·        All server-generated alerts

·        Automatic SGAMemory Management

·        Automatic optimizer statistics collection

·        Object level statistics

·        End to End Application Tracing (

V$CLIENT_STATS

)

·        Database time distribution statistics (

V$SESS_TIME_MODEL

 and 

V$SYS_TIME_MODEL

)

·        Service level statistics

·        Buffer cache advisory

·        MTTR advisory

·        Shared pool sizing advisory

·        Segment level statistics

·        PGA Target advisory

·        Timed statistics

·        Monitoring of statistics

 

Answer:CE

134 - RMAN section size

You are managing an Oracle Database 11g database. You want to takea backup on tape drives of the USERS tablespace that has a single data file of900 MB. You have tape drives of 300 MB each. To accomplish the backup, youissued the following RMAN
command:
RMAN>BACKUP
SECTION SIZE 300M
TABLESPACE users;
What configuration should be effected to accomplish faster andoptimized backups by using the above command?
A. The SBT channel must be configured, with the defaultparallelism setting for the SBT device set to 1.
B. The COMPATIBLE initialization parameter for the databaseinstance must be set to at least 10.0.
C. The SBT channel must be configured, with the parallelismsetting for the SBT device set to 3.
D. The SBT channel must be configured, with the MAXPIECESIZE setto 300 MB.
 
解析:

参考146题
http://docs.oracle.com/cd/B28359_01/backup.111/b28270/rcmbckad.htm#BRADV89546
Dividing the Backup of aLarge Datafile into Sections

If you specify the 

SECTION SIZE

 parameter
on the 

BACKUP

 command, then RMAN creates a backup set in which each backup piececontains the blocks from one file section. A file
section is a contiguous range of blocks in a file. This type of backup iscalled a multisection
backup.

Note:

You cannot specify 

SECTION SIZE

 in conjunction with 

MAXPIECESIZE

.

The purpose of multisectionbackups is to enable RMAN channels to back up a single large file in parallel. RMANdivides the work among multiple channels, with each channel backing up one filesection
in a file. Backing up a file in separate sections can improve theperformance of backups of large datafiles.

If a multisectionbackup completes successfully, then none of the backup sets generated duringthe backup contain a partial datafile. If a multisection backup is unsuccessful,then it is possible
for the RMAN metadata to contain a record for a partialbackup set. RMAN does not consider partial backups for restore and recovery. Youmust use the 

DELETE

 command
todelete the partial backup set.

If you specify a sectionsize that is larger than the size of the file, then RMAN does not usemultisection backup for the file. If you specify a small section size that wouldproduce more than
256 sections, then RMAN increases the section size to a valuethat results in exactly 256 sections.

To make a multisection backup:

Start RMANand connect to a target database and recovery catalog (if used).

If necessary,configure channel parallelism so that RMAN can parallelize the backup.

Execute 

BACKUP

 with
the 

SECTION SIZE

 parameter.

For example,suppose that the 

users

 tablespace contains a single datafile of 900 MB. Also
assumethat three SBT channels are configured, with the parallelism setting for theSBT device set to 3. You can break up the datafile in this tablespace into filesections as shown in the following example:

BACKUP

  SECTION SIZE 300M

  TABLESPACE users;

In thisexample, each of the three SBT channels backs up a 300 MB file section of the 

users

 datafile.

http://docs.oracle.com/cd/B28359_01/backup.111/b28270/rcmvalid.htm#BRADV89564
Parallelizing the Validationof a Datafile

If you need to validate a large datafile, then RMAN canparallelize the work by dividing
the file into sections and processing each file
section in parallel. If multiple channels areconfigured or allocated, and if you want the channels to parallelize thevalidation, then specify the 

SECTIONSIZE

 parameter
ofthe  

VALIDATE

 command.

If you specify asection size that is larger than the size of the file, then RMAN does notcreate file sections. If you specify a small section size that would producemore than 256 sections, then RMAN increases the section
size to a value thatresults in exactly 256 sections.

To parallelize the validation of a datafile:

Start RMANand connect to a target database. The target database must be mounted or open.

Run 

VALIDATE

 with the 

SECTIONSIZE

 parameter.

Thefollowing example allocates two channels and validates a large datafile. The sectionsize is 1200 MB.

RUN

{

  ALLOCATE CHANNEL c1 DEVICE TYPE DISK;

  ALLOCATE CHANNEL c2 DEVICE TYPE DISK;

 VALIDATE DATAFILE 1 SECTION SIZE 1200M;

}

 
Maxpiecesize与 section size区别
maxsetsize及maxpiece侧重点不一样

一个数据库的备份是由多个backup set组成的，一个backup set 可能是由多个piece组成的。

maxsetsize的设定更多侧重的是优化，它定义了一个backupset的大小，从而rman就会自动的控制这个backup set包含多少个datafile或archive log等文件。其作用是与filesperset差不多的。

maxpiecesize侧定的是限制,因为实际生成的文件是piece，如果你的文件系统不支持大文件，最大的文件则为2GB，当然要做maxpiecesize的设定，不然会报错。
 
If you specify the 

SECTION SIZE

 parameter on the 

BACKUP

 command,
then RMAN produces a multisection
backup. This is a backup of a single large file, produced by multiple channelsin parallel, each of which produces one backup piece. Each backup piececontains one file
section of thefile being backed up.
 
http://docs.oracle.com/cd/B28359_01/backup.111/b28270/glossary.htm#BRADV90209

multisectionbackup
An RMAN backupset in which each backup piece containsa file
section, which is acontiguous range of blocks in a datafile. Note that a multisection backup
set containsmultiple backup pieces, but a backup set never contains only a part of adatafile.
You create amultisection backup by specifying the SECTION SIZE parameter on the BACKUP command.
An RMAN channel canprocess each file
section independently, either serially or in parallel. Thus,in a multisection backup, multiple channels can back up a single file.
 

Answer: C

228 - Partitions Reference-Partitioned Tables

Evaluate the following statements:
CREATE TABLE purchase_orders (po_id NUMBER(4),
po_date TIMESTAMP, supplier_id NUMBER(6), po_total NUMBER(8,2),
CONSTRAINT order_pk PRIMARY KEY(po_id))
 PARTITION BY RANGE(po_date)
(PARTITION Q1 VALUES LESS THAN (TO_DATE(?1-apr-2007?d-mon-yyyy?),
 PARTITION Q2 VALUES LESSTHAN (TO_DATE(?1-jul-2007?d-mon-yyyy?),
PARTITION Q3 VALUES LESS THAN (TO_DATE(?1-oct - 2007?d-mon-yyyy?),
PARTITION Q4 VALUES LESS THAN (TO_DATE(?1-jan-2008?d-mon-yyyy?));
 
CREATE TABLE purchase_order_items (po_id NUMBER(4) NOT NULL,product_id NUMBER(6) NOT NULL, unit_price NUMBER(8,2), quantity NUMBER(8),
CONSTRAINT po_items_fk FOREIGN KEY (po_id)
REFERENCESpurchase_orders(po_id)) PARTITION BY
REFERENCE(po_items_fk);
What are the two consequences of the above statements? (Choosetwo.)
A. Partitions of PURCHASE_ORDER_ITEMS have system-generated names.
B. Both PURCHASE_ORDERS and PURCHASE_ORDER_ITEMS tables arecreated with four partitions each.
C. Partitions of the PURCHASE_ORDER_ITEMS table exist in the sametablespaces as the partitions of the PURCHASE_ORDERS table.
D. The PURCHASE_ORDER_ITEMS table inherits the partitioning keyfrom the parent table by
automatically duplicating the key columns.
E. Partition maintenance operations performed on thePURCHASE_ORDER_ITEMS table are
automatically reflected in the PURCHASE_ORDERS table.
 

解析:

http://docs.oracle.com/cd/E11882_01/server.112/e25523/part_admin001.htm#BAJDDEEC

CreatingReference-Partitioned Tables

To create areference-partitioned table, you specify a 

PARTITION BY REFERENCE

 clause
in the 

CREATE TABLE

 statement. This clause specifies the name of a referentialconstraint and this constraint becomes the partitioning referential
constraintthat is used as the basis for reference partitioning in the table. Thereferential constraint must be enabled and enforced.

As with otherpartitioned tables, you can specify object-level default attributes, and youcanoptionally specify partition descriptors thatoverride the object-level defaults
on a per-partition basis.

Example 4-9 creates a parent
table 

orders

 which is range-partitioned on 

order_date

.
Thereference-partitioned child table 

order_items

 is created with four partitions, 

Q1_2005

, 

Q2_2005

, 

Q3_2005

,
and 

Q4_2005

, where eachpartition contains the 

order_items

 rows
corresponding to orders in the respective parent partition.

Example 4-9 Creatingreference-partitioned tables

CREATE TABLE orders

    ( order_id           NUMBER(12),

      order_date         TIMESTAMP WITH LOCAL TIME ZONE,

      order_mode         VARCHAR2(8),

      customer_id        NUMBER(6),

      order_status       NUMBER(2),

      order_total        NUMBER(8,2),

      sales_rep_id       NUMBER(6),

      promotion_id       NUMBER(6),

      CONSTRAINT orders_pk PRIMARY KEY(order_id)

    )

  PARTITION BY RANGE(order_date)

    ( PARTITION Q1_2005 VALUES LESS THAN (TO_DATE('01-APR-2005','DD-MON-YYYY')),

      PARTITION Q2_2005 VALUES LESS THAN (TO_DATE('01-JUL-2005','DD-MON-YYYY')),

      PARTITION Q3_2005 VALUES LESS THAN (TO_DATE('01-OCT-2005','DD-MON-YYYY')),

      PARTITION Q4_2005 VALUES LESS THAN (TO_DATE('01-JAN-2006','DD-MON-YYYY'))

    );

CREATE TABLE order_items

    ( order_id           NUMBER(12) NOT NULL,

      line_item_id       NUMBER(3)  NOT NULL,

      product_id         NUMBER(6)  NOT NULL,

      unit_price         NUMBER(8,2),

      quantity           NUMBER(8),

      CONSTRAINT order_items_fk FOREIGN KEY(order_id) REFERENCES orders(order_id)

    )

    PARTITION BY REFERENCE(order_items_fk);

If partitiondescriptors are provided, then
the number ofpartitions described must exactly equal the number of partitions orsubpartitions in the referenced table. If the parent tableis a composite partitioned table, then the
table has one partition for eachsubpartition of its parent; otherwise the table has one partition for eachpartition of its parent.

Partition bounds cannotbe specified for the partitions of a reference-partitioned table.

The partitions of areference-partitioned table can be named. If a partition is not explicitlynamed, thenit inherits its name fromthe corresponding partition in the parent table,
unless this inheritedname conflicts with an existing explicit name. In this case, the partition hasasystem-generatedname.

Partitions of areference-partitioned table collocate with the corresponding partition of theparent table, if no explicit tablespace is specified for thereference-partitioned table's partition.

Answer:AB

229 - LOBs SecureFile

Which statements are true regardingSecureFileLOBs?
(Choose all thatapply.)
A. The amount of undo retained is user controlled.
B. SecureFile LOBs can be used only for nonpartitioned tables.
C. Fragmentation is minimized by using variable-sized chunksdynamically.
D. SecureFile encryption allows for random reads and writes of theencrypted datA.
E.
Itautomatically detects duplicate LOBdata and conserves space by storing only one copy.
 

解析:

http://docs.oracle.com/cd/E11882_01/appdev.112/e10777/ch_dba.htm#IMURG11681

SecureFile LOBs andBasicFile LOBs

SecureFile LOBs(SecureFiles) were introduced in Oracle Database 11g Release 1 (11.1) tosupplement the original BasicFile LOBs implementation that is identified by theSQL parameter BASICFILE. The performance of SecureFile LOBs
is significantlybetter than that of BasicFile LOBs, especially for large media data. Oraclerecommends using SecureFile LOBs for storing media data whenever possible. SecureFileLOBs are identified by specifying the SQL parameter SECUREFILE.

http://docs.oracle.com/cd/E11882_01/appdev.112/e10764/lobs.htm#LNCPP20341

Using SecureFile Compression

SecureFiles compressionenables server-side compression of LOB data, transparent to the application.Using SecureFiles compression saves storage space with minimal impact onreading and updating performance for SecureFiles LOB data.

Using SecureFiles Encryption

SecureFiles introduce anew encryption capability for LOB data and extend Transparent Data Encryptionby enabling efficient random read and write access to encrypted SecureFiles LOBs.

Using SecureFiles Deduplication

SecureFiles deduplicationallows the Oracle Database to automaticallydetect duplicate LOB data,and to conserve space by storing a single copy of the SecureFiles LOB.

http://docs.oracle.com/cd/E11882_01/appdev.112/e18294/adlob_smart.htm#ADLOB45162

About SecureFiles LOBs

Beginning with OracleDatabase 11g Release1, Oracle introduced SecureFiles, a new LOB storage architecture. SecureFilesLOBs are created when the storage keyword 

SECUREFILE

 appears
in the 

CREATE

 

TABLE

 statement. The original LOB storage
architecture, BasicFilesLOBs, is the default storage. It is in effect if the keyword 

SECUREFILE

 is not used, or if the keyword 

BASICFILE

 is
used in the 

CREATE

 

TABLE

 statement.

The following sectionsdescribe LOB storage characteristics used when designing, creating, andmodifying tables with LOB column types. The database administrator may use the 

db_securefile

 initialization
parameter in the 

init.ora

 file to modify initial settings.

Oracle recommends thatyou enable compression, deduplication, or encryption through the 

CREATE TABLE

 statement.
If you enable these features through the

ALTER TABLE

 statement, all SecureFilesLOB data in the table is read, modified, and
written; this causes the databaseto lock the table during a potentially lengthy operation.

This section containsthe following topics:

·        About Compression

·        About Deduplication

·        About Encryption

About Compression

SecureFiles IntelligentCompression, available with the Oracle Advanced Compression Option, seamlesslyanalyzes SecureFiles LOB data and compresses to save disk space.

Note that you must havea license for the Oracle Advanced Compression Option before implementing SecureFilesIntelligent Compression. See Oracle
DatabaseLicensing Information for moreinformation.

AboutDeduplication

SecureFiles IntelligentDeduplication, available with the Oracle Advanced Compression Option, enablesOracle Database toautomatically detect duplicate LOB data within a LOB column orpartition, and
conserve space by storing only one copy of the data.

Note that you must havea license for the Oracle Advanced Compression Option before implementingSecureFiles Intelligent Deduplication. See OracleDatabase
Licensing Information for more information.

Note also that OracleStreams does not support SecureFiles LOBs that are deduplicated.

About Encryption

SecureFiles IntelligentEncryption, available with the Oracle Advanced Security Option, introduces anew encryption facility for LOBs. The data is encrypted using Transparent DataEncryption (TDE), which allows the data to be stored
securely, and still allowsfor random read and write access.

Note that you must havea license for the Oracle Advanced Security Option before implementingSecureFiles Intelligent Encryption. See OracleDatabase
Licensing Information for more information.

http://docs.oracle.com/cd/E11882_01/appdev.112/e18294/adlob_smart.htm#ADLOB45947

CHUNK

CHUNK

 is one or more Oracle blocks. For SecureFiles LOBs, 

CHUNK

 is
an advisory size and is provided for backward compatibilitypurposes. For BasicFiles LOBs, you may specify the chunk size when creating atable that stores LOBs; it corresponds to the data size used by Oracle Databasewhen accessing or modifying the LOB value.


Answer:CDE