How to estimated time for oracle sql query

Question

i have query run every month on production server to collect some information
data size is difference every month
what i need to estimate the time before running
how can i do that

Answer 1

sorry this is what i get
when i caculate time column it give me 10 sec
but when i make this
SQL> set timing on;
SQL> select * from tab;
3658 rows selected.
Elapsed: 00:00:05.50
so whay in the first give me 10 sec and the secand give me 5.50 sec
SQL> explain plan for select * from tab;
Explained.
SQL> select * from table(dbms_xplan.display);
PLAN_TABLE_OUTPUT
Plan hash value: 457676135
| Id | Operation | Name | Rows | Bytes | Cost (%CPU)| Time |
| 0 | SELECT STATEMENT | | 1243 | 104K| 182 (4)| 00:00:03 |
| 1 | NESTED LOOPS OUTER | | 1243 | 104K| 182 (4)| 00:00:03 |
|* 2 | TABLE ACCESS FULL | OBJ$ | 1243 | 98197 | 142 (5)| 00:00:02 |
| 3 | TABLE ACCESS CLUSTER| TAB$ | 1 | 7 | 1 (0)| 00:00:01 |
|* 4 | INDEX UNIQUE SCAN | I_OBJ# | 1 | | 0 (0)| 00:00:01 |
PLAN_TABLE_OUTPUT
Predicate Information (identified by operation id):
2 - filter("O"."TYPE#"<=5 AND "O"."OWNER#"=USERENV('SCHEMAID') AND
"O"."TYPE#">=2 AND "O"."LINKNAME" IS NULL)
4 - access("O"."OBJ#"="T"."OBJ#"(+))
18 rows selected.
SQL>
Edited by: 862640 on Nov 27, 2011 1:43 AM
Edited by: 862640 on Nov 27, 2011 1:49 AM
Edited by: 862640 on Nov 27, 2011 1:53 AM