105.Which statements are true regarding table compression? (Choose all that apply.)
A. It saves disk space and reduces memory usage.
B. It saves disk space but has no effect on memory usage.
C. It incurs extra CPU overhead during DML as well as direct loading operations.
D. It incurs extra CPU overhead during DML but not direct loading operations.
E. It requires uncompress operation during I/O.
Answer: AC
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/tables.htm#ADMIN11630
A. It saves disk space and reduces memory usage.
B. It saves disk space but has no effect on memory usage.
C. It incurs extra CPU overhead during DML as well as direct loading operations.
D. It incurs extra CPU overhead during DML but not direct loading operations.
E. It requires uncompress operation during I/O.
Answer: AC
A、它节省了磁盘空间，减少了内存的使用。
B、它节省了磁盘空间，但对内存的使用没有影响。
C、它会带来额外的CPU开销在DML以及直接加载操作。
D、它会带来额外的CPU开销在DML但不直接加载操作。
E、它要求在I/O时解压缩操作。
参考：http://docs.oracle.com/cd/E11882_01/server.112/e25494/tables.htm#ADMIN11630
当您的数据库规模增长时，请考虑使用表压缩。
压缩节省了磁盘空间，减少了在数据库缓存中的内存使用，并且可以在读取过程中显着加快查询的执行速度。
对于数据加载和DML操作，数据压缩会有CPU的开销成本。
然而，这个成本可能会被减少I/O的要求所抵消。
来自 “ ITPUB博客 ” ，链接：https://blog.itpub.net/81227/viewspace-2117515/ ，如需转载，请注明出处，否则将追究法律责任。
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