OCP 1Z0 052 24

24. Which  two statements correctly describe  the  relation between a data  file and  the  logical database 
structures? (Choose two.) 
A.An extent cannot spread across data files. 
B.A segment cannot spread across data files. 
C.A data file can belong to only one tablespace. 
D.A data file can have only one segment created in it. 
E.A data block can spread across multiple data files as it can consist of multiple operating system (OS)  blocks. 
Answer: AC   

An extent is a logical unit of database storage space allocation made up of contiguous data blocks.
区（extent ）是连续的块（data block），不能跨文件。

A segment is a set of extents that contains all the data for a logical storage structure within a tablespace.
但段（segment ）不需要连续。

一个数据文件只能属于一个表空间，一个表空间可以有多个数据文件

一个数据文件可以有多个不同的段

数据块是最小的单位，是os块的倍数，但不能跨文件。