To check performance of query through sqlplus command prompt

  

Here's explain plan:

SQL> explain plan for

  2  select * from emp; 

Explained.

SQL> select * from table(dbms_xplan.display());

PLAN_TABLE_OUTPUT

-----------------------------------------------------------------------------------------------

Plan hash value: 1833546154

---------------------------------------------------------------------------------------------

| Id  | Operation                   | Name          | Rows  | Bytes | Cost (%CPU)| Time     |

---------------------------------------------------------------------------------------------

|   0 | SELECT STATEMENT            |               |     1 |    69 |     1   (0)| 00:00:01 |

|   1 |  TABLE ACCESS BY INDEX ROWID| EMPLOYEES     |     1 |    69 |     1   (0)| 00:00:01 |

|*  2 |   INDEX UNIQUE SCAN         | EMP_EMP_ID_PK |     1 |       |     0   (0)| 00:00:01 |

---------------------------------------------------------------------------------------------

Or

You can also use autotrace option:

SQL> set autotrace on

SQL> select * from emp;