How do you get the explain plan? Can some one please explain a bit about explain plan, and how does one get the explain plan for a query. Also, if there is any sql script which can be used as utility for this, that would be great.
You can use the package DBMS_XPLAN:

SQL&gt; explain plan for select * from dual;

Explained

SQL&gt; select * from table(dbms_xplan.display);

PLAN_TABLE_OUTPUT
--------------------------------------------------------------------------------
--------------------------------------------------------------------
| Id  | Operation            |  Name       | Rows  | Bytes | Cost  |
--------------------------------------------------------------------
|   0 | SELECT STATEMENT     |             |     1 |     2 |     2 |
|   1 |  TABLE ACCESS FULL   | DUAL        |     1 |     2 |     2 |
--------------------------------------------------------------------
Note: cpu costing is off