Hi All, This is just question for curiosity. May be i am wrong but please help me in understanding this. Below is the details where i am using one test table created from dba_objects. What i did is i ran first select * from test and the other one with pstop that pid from different session. Both are almost same. Also i had flushed shared/buffer cache 2-3 time before each test. So, both are doing same. DB Version : 10.2.0.3 Solaris SPARC 64 SEGMENT_NAME BYTES BLOCKS ---------------------------------- ---------- ---------- TEST 6291456 384 Statistics (From select * from test without pstop) ---------------------------------------------------------- 504 recursive calls 0 db block gets 3714 consistent gets 341 physical reads 0 redo size 2611800 bytes sent via SQL*Net to client 36512 bytes received via SQL*Net from client 3277 SQL*Net roundtrips to/from client 4 sorts (memory) 0 sorts (disk) 49128 rows processed Statistics (From select * from test with 2 times pstop) ---------------------------------------------------------- 504 recursive calls 0 db block gets 3714 consistent gets 343 physical reads 0 redo size 2611800 bytes sent via SQL*Net to client 36512 bytes received via SQL*Net from client 3277 SQL*Net roundtrips to/from client 4 sorts (memory) 0 sorts (disk) 49128 rows processed But from mystat there is a difference. Here is how i had ran set autotrace on; alter system flush shared_pool; alter system flush buffer_cache; create table x1 as select sn.name, ms.value from v$mystat ms, v$statname sn where ms.statistic# = sn.statistic# ; select * from test; create table x2 as select sn.name, ms.value from v$mystat ms, v$statname sn where ms.statistic# = sn.statistic# ; select y1.name,y1.value,y2.value,y2.value-y1.value from y1,y2 where y1.name= y2.name order by 1; From 1st and 2nd result there is difference with. First Second physical read bytes 6504448 10633216 physical read total IO requests 84 332 physical read total bytes 6569984 10698752 physical read total multi block requests 28 29 physical reads 397 649 physical reads cache 397 649 physical reads cache prefetch 317 321 physical reads prefetch warmup 21 25 recursive calls 4021 16397 sorts (memory) 71 332 sorts (rows) 420 2071 table fetch by rowid 862 1858 execute count 299 1116 So, is it saying that it's revisiting all blocks again but not showing in autotrace. -- Thanks & Regards, Taral Desai Pablo Picasso<http://www.brainyquote.com/quotes/authors/p/pablo_picasso.html> - "Computers are useless. They can only give you answers."