053试题 229 / 239- securefile lobs

题目：

229.Which statements are true regarding SecureFile LOBs? (Choose all that apply.)
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 chunks dynamically.
D. SecureFile encryption allows for random reads and writes of the encrypted data.
E. It automatically detects duplicate LOB data and conserves space by storing only one copy.

参考答案 CD
保留的undo由系统控制。A错误。
secure file可以使用于分区表和非分区表。B错误。
通过动态使用可变大小的块，可以最小化碎片。C正确。

选项E，要在建表的时候指定是否duplicate。

参考文档：

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

FREEPOOLS

Specifies the number of FREELIST groups for BasicFiles LOBs, if the database is in automatic undo mode. Not used for SecureFiles LOBs.

https://docs.oracle.com/cd/E11882_01/appdev.112/e18294/adlob_smart.htm#ADLOB46111

About Encryption

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

Note that you must have a license for the Oracle Advanced Security Option before implementing SecureFiles Intelligent Encryption. See Oracle Database Licensing Information for more information.

About Deduplication

SecureFiles Intelligent Deduplication, available with the Oracle Advanced Compression Option, enables Oracle Database to automatically detect duplicate LOB data within a LOB column or partition, and conserve space by storing only one copy of the data.

Note that you must have a license for the Oracle Advanced Compression Option before implementing SecureFiles Intelligent Deduplication. See Oracle Database Licensing Information for more information.

Note also that Oracle Streams does not support SecureFiles LOBs that are deduplicated.

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题目：

239.Evaluate the following command:
SQL>ALTER SYSTEM SET db_securefile = 'IGNORE';
What is the impact of this setting on the usage of SecureFiles?
A. It forces BasicFiles to be created even if the SECUREFILE option is specified to create the LOB.
B. It forces SecureFiles to be created even if the BASICFILE option is specified to create the LOB.
C. It does not allow the creation of SecureFiles and generates an error if the SECUREFILE option is specified to create the LOB.
D. It ignores the SECUREFILE option only if a Manual Segment Space Management tablespace is used and creates a BasicFile.

参考答案 A
解析
题目意思是，设置了db_securefile为ignore。对使用securefile有什么影响。
如果指定了IGNORE，则忽略SECUREFILE关键字和所有SecureFiles LOB选项。选择A 。

参考文档：

https://docs.oracle.com/cd/E11882_01/appdev.112/e18294/adlob_smart.htm#ADLOB45228

Initialization Parameter db_securefile for SecureFiles LOBs

The initialization parameter db_securefile is set in the file init.ora.

The parameter db_securefile is of type text. Its allowable values are ALWAYS, PERMITTED [default], NEVER, or IGNORE. The db_securefile parameter is dynamic and its scope is ALTER SYSTEM.

Example 4-26 Setting db_securefile parameter through ALTER SYSTEM

ALTER SYSTEM SET db_securefile = 'ALWAYS';

The db_securefile parameter enables the database administrator to either allow SecureFiles LOBs to be created (PERMITTED), disallow SecureFiles LOBs from being created in the future (NEVER), attempt to create SecureFiles LOBs but fall back to BasicFiles LOBs (ALWAYS), or disallow SecureFiles LOBs and ignore any errors that would otherwise be caused by forcing BasicFiles LOBs with SecureFiles LOBs options (IGNORE).

If NEVER is specified, any LOBs that are specified as SecureFiles LOBs are created as BasicFiles LOBs. All SecureFiles LOB- specific storage options and features such as compress, encrypt, or deduplicate throw an exception. The BasicFiles LOB defaults are used for storage options not specified.

ALWAYS attempts to create all LOBs as SecureFiles LOBs but creates any LOBs not in ASSM tablespaces as BasicFiles LOBs, unless the SECUREFILE parameter is explicitly specified. Any BasicFiles LOB storage options specified are ignored, and the SecureFiles LOB defaults are used for all storage options not specified.

If IGNORE is specified, the SECUREFILE keyword and all SecureFiles LOB options are ignored.

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