title: True tablespace size in oracle
body: <p>I need to know <em>true</em> tablespace size in Oracle. I have some tablespace and I need to know how many space it uses now and how many space is free (and maybe percent of free space). I found in web some sqls but all of them showed size based on water mark... which is not true space allocated now but as far as I know the highest value which has ever been reached... 
  So my real need is to know if I have enough space for my data which constantly are written and I must know how much of them I can store before having to delete some of them.</p>
  
  <p>Thanks</p>