Oracle OCP 1Z0-050（36题）解析

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Oracle OCP 1Z0-050（36题）解析

QUESTION 36:

Evaluate the following command:

SQL> CREATE TABLE design_data (id NUMBER,

doc CLOB)

LOB(doc) STORE AS SECUREFILE(DEDUPLICATE);

Which statement is true regarding the above command?

A. All LOB data that is identical in two or more rows in a LOB column share the same data blocks.

B. The LOB values are cached by default in the buffer cache.

C. The LOB values are automatically stored in encrypted mode.

D. The LOB values are automatically compressed.

Answer: A

解析：

https://docs.oracle.com/cd/B28359_01/appdev.111/b28393/adlob_what.htm#i972443

LOB Features Introduced in Oracle Database 11g Release 1

Oracle SecureFiles adds the following capabilities:

• Intelligent LOB compression enables users to explicitly compress data to save disk space. This feature can only be used with the new LOB implementation in this release (storage parameter SECUREFILE).

• Intelligent LOB encryption introduces a new encryption facility for LOBs. The encrypted data in now stored in-place and is available for random reads and writes. This feature can only be used with the new LOB implementation in this release (storage parameter SECUREFILE).

• Deduplication enables Oracle Database to automatically detect duplicate LOB data and conserve space by only storing one copy (storage parameter SECUREFILE).

• LOB data path optimization includes logical cache above storage layer, read prefetching, new caching modes, vectored IO, and so on.

• New LOB APIs. Existing OCI functions work on the new SECUREFILE LOBs. New OCI functions and PL/SQL packages are also added. Parameters of the CREATE TABLE, ALTER TABLE, and SQL commands are new or changed for LOBs. High performance space management includes changes to LOB SQL statements and DBMS_SPACE package changes.