1.oracle pctfree和pctused详解
http://www.cnblogs.com/linjiqin/archive/2012/01/16/2323320.html
http://blog.csdn.net/huang_xw/article/details/6995442
http://www.cnblogs.com/linjiqin/archive/2012/01/16/2323320.html
http://blog.csdn.net/huang_xw/article/details/6995442