Oracle 11g: Oracle insert/update operation is taking more time.

Question

Hello All,
In Oracle 11g (Windows 2008 32 bit environment) we are facing following issue.
1) We are inserting/updating data on some tables (4-5 tables and we are firing query with very high rate).
2) After sometime (say 15 days with same load) we are feeling that the Oracle operation (insert/update) is taking more time.
Query1: How to find actually oracle is taking more time in insert/updates operation.
Query2: How to rectify the problem.
We are having multithread environment.
Thanks
With Regards
Hemant.

Answer 1

Liron Amitzi wrote:
Hi Nicolas,
Just a short explanation:
If you have a table with 1 column (let's say a number). The table is empty and you have an index on the column.
When you insert a row, the value of the column will be inserted to the index. To insert 1 value to an index with 10 values in it will be fast. It will take longer to insert 1 value to an index with 1 million values in it.
My second example was if I take the same table and let's say I insert 10 rows and delete the previous 10 from the table. I always have 10 rows in the table so the index should be small. But this is not correct. If I insert values 1-10 and then delete 1-10 and insert 11-20, then delete 11-20 and insert 21-30 and so on, because the index is sorted, where 1-10 were stored I'll now have empty spots. Oracle will not fill them up. So the index will become larger and larger as I insert more rows (even though I delete the old ones).
The solution here is simply revuild the index once in a while.
Hope it is clear.
Liron Amitzi
Senior DBA consultant
[www.dbsnaps.com]
[www.orbiumsoftware.com]Hmmm, index space not reused ? Index rebuild once a while ? That was what I understood from your previous post, but nothing is less sure.
This is a misconception of how indexes are working.
I would suggest the reading of the following interasting doc, they are a lot of nice examples (including index space reuse) to understand, and in conclusion :
http://richardfoote.files.wordpress.com/2007/12/index-internals-rebuilding-the-truth.pdf
"+Index Rebuild Summary+
+•*The vast majority of indexes do not require rebuilding*+
+•Oracle B-tree indexes can become “unbalanced” and need to be rebuilt is a myth+
+•*Deleted space in an index is “deadwood” and over time requires the index to be rebuilt is a myth*+
+•If an index reaches “x” number of levels, it becomes inefficient and requires the index to be rebuilt is a myth+
+•If an index has a poor clustering factor, the index needs to be rebuilt is a myth+
+•To improve performance, indexes need to be regularly rebuilt is a myth+"
Good reading,
Nicolas.