问题源至：http://www.itpub.net/thread-956623-1-1.html
内容如下：
free space 大于db file的大小

遇到一个奇怪的问题， db file free space的大小大于file的大小。导致在toad下看到的使用率为负的

select sum(bytes) from dba_free_space where file_id=8;
result: 35672489984 (这个大小已经达到了数据文件的max)

select bytes from dba_data_files where file_id=8;
result: 10171187200

这种问题，一般情况下，可以往bug上去考虑，后来和puber在msn上聊，得知是Oracle 10.2.0.2,
正好我的客户的Oracle版本都是这个，所以就去查了一下，结果和预料的一样，是一个bug所致。

Details:
The values of FILE_ID / REL_FNO may be wrong in DBA_FREE_SPACE if a table has been dropped but exists in the RECYCLE BIN

Workaround: Purge the dropped table from the recycle bin.

When the table is dropped that the freed up space is accounted for in the wrong datafile and hence we see the size of datafile bigger than its defined size. If you purge the recyclebin then the incorrect accounting is fixed.

Solution
This bug is fixed in next release of Oracle 11 and is also fixed in upcoming patchsets 10.2.0.4 & 10.1.0.6. There are few one-off patches available, please check metalink for existence of one-off patch for your patchset level and OS platform.

As a simple workaround you can purge the dropped table from the recycle bin.

最后，也是建议puber通过查询dba_recyclebin并purge后问题解决,这个版本上的bug真不是一般的少啊。