1. I create every MV based on the proper tables and specify the initial extend size properly .
2. There are still 1GB data in the tablespace which allocate to the MVs
3. The Master Tables changed very few .
4. The Refresh is 'Fast' mode
5. Sometime , the refresh action will cause the oracle error ,
the tablespace [My MV Tablespace] can not extent XXXX

How to investigate in this case ?