Oracle DB , 计算各个用户/schema 的磁盘占用空间
http://www.dba-oracle.com/t_find_size_schema.htm
Question: How do I find the size of a schema in my database?
Answer: It depends on how you define "size". If you want the total disk space consumed by the schema (including indexes, tablespace free space), then the SQL query is quite simple:
select owner, sum(bytes)/1024/1024/1024 schema_size_gig from dba_segments group by owner;
If you just want the size of the schema in terms of the space consumed by table rows, you would use a different query to calculate the schema size:
select sum(bytes)/1024/1024/1024 as size_in_gig, segment_type from dba_segments where owner='SCOTT' group by segment_type;
Drop Table 之后,如果空间不能回收,需要执行西面语句
清除当前用户的回收站:purge recyclebin;
清除所有用户的回收站:purge dba_recyclebin;