oracle查询表空间总大小(DBA_DATA_FILES和DBA_SEGMENTS,DBA_FREE_SPACE区别)

1, dba_data_files,dba_segments,dba_free_space
得出结论:一般情况下(没有drop表的时候):dba_data_files bytes = (dba_segments bytes + dba_free_space bytes)

实验:

SQL> Select sum(bytes)/1024/1024/1024 from dba_segments;
SUM(BYTES)/1024/1024/1024
————————-
           1.58441162

SQL> select sum(bytes)/1024/1024/1024 from dba_free_space;
SUM(BYTES)/1024/1024/1024
————————-
           .323669434

SQL> select sum(bytes)/1024/1024/1024 from dba_data_files;
SUM(BYTES)/1024/1024/1024
————————-
        1.9140625