052(二十七）

131.You execute a command to resize a data file, sales.dbf, of size 200 MB in your database:
ALTER DATABASE DATAFILE '/remorse/sales.dbf' RESIZE 150M;
Which statement is true about this command?
A. The command must be issued in MOUNT state.
B. The command succeeds only if the data file is offline.
C. The command must be issued when the database is in the archivelog mode.
D. The command succeeds if no extent in the tablespace is currently allocated above the 150 MB boundary of the file.

Answer: B

实例启动时如有需要，系统监控进程（system monitor process，SMON）将负责进行恢复（recovery）工作。此外，SMON 还负责清除系统中不再使用的临时段（temporary segment），以及为数据字典管理的表空间（dictionary managed tablespace）合并相邻的可用数据扩展（extent）。