Order by in sql query

Question

I am executing one sql query with order by clause.
how to check sort is happing in memory or disk ?
what are all the init parameter affect in order by clause

Answer 1

There are a couple of ways.
1. Query the V$MYSTAT view before and after your query and take the delta of the statistics. A query to retrieve sort information could be the following:
SELECT name,value FROM V$mystat m JOIN v$statname USING (statistic#) where name like 'sorts%';2. In SQL*Plus Set AUTOTRACE TO STATISTICS and run your query. The sort information will be at the bottom.
Sample:
SQL > set autotrace off;
SQL > SELECT name,value FROM V$mystat m JOIN v$statname USING (statistic#) where name like 'sorts%';
NAME                                                                  VALUE
sorts (memory)                                                           12
sorts (disk)                                                              0
sorts (rows)                                                             42
SQL > SET AUTOTRACE TRACEONLY STATISTICS
SQL > SELECT * FROM (SELECT OBJECT_NAME FROM ALL_OBJECTS WHERE ROWNUM <= 100) ORDER BY OBJECT_NAME;
100 rows selected.
Statistics
        674  recursive calls
          0  db block gets
        245  consistent gets
          0  physical reads
          0  redo size
       2257  bytes sent via SQL*Net to client
        462  bytes received via SQL*Net from client
          8  SQL*Net roundtrips to/from client
         31  sorts (memory)
          0  sorts (disk)
        100  rows processed
SQL > SET AUTOTRACE OFF;
SQL > SELECT name,value FROM V$mystat m JOIN v$statname USING (statistic#) where name like 'sorts%';
NAME                                                                  VALUE
sorts (memory)                                                           43
sorts (disk)                                                              0
sorts (rows)                                                            173HTH!