title: understanding tracefile generated from tkprof
body: <p>hey guys i am learning query optimization with oracle 10g, and having some trouble understanding the file below.
  could some anyone please explain the file below, its a trace file of query i ran.
  i know what CPU and elapsed time is (time a query takes to fetch data from database) 
  but unsure about "disk" and "query".</p>
  
  <pre><code>call     count       cpu    elapsed       disk      query    current  rows
  ------- ------  -------- ---------- ---------- ---------- ----------  -------
  Parse        1      0.00       0.00          0          0          0     0
  Execute      1      0.00       0.00          0          0          0     0
  Fetch     9001      0.17       0.15       1812      16205          0   134999
  ------- ------  -------- ---------- ---------- ---------- ----------  -------
  total     9003      0.17       0.15       1812      16205          0   134999
  </code></pre>