Performance Questions

1)  What is log sync wait event ?

2)  AWR reports ? 

      --> What are the things you check for in an AWR report ?

      --> Where do you check for issues in an AWR report ?

3) To 10 wait events , and how do you resolve them ?

4) Batch job was running fine till yesterday, today its taking long. What are the things you will check for?

5) When do indexes become invalid ?

6) For regular jobs why the Hash-Plan-Value gets changed suddenly and job takes long time ?

7) What are the things you check for when user's complain of performance issues ?

8) What is an explain plan and what do you check in it to resolve performance issues ?

9) What is ASH and what can we get from it? What is the difference between AWR and ASH ?

10) I have a 20GB of update/insert statements and my SGA is only 5 GB . How does it work ?

11) How do avoid parsing ?

12) Query is running slow. Can we force to change the execution plan ?

13) WAIT events , Type of wait events and locks and types of locks ?

14) How is a query PARSED in oracle database ?

15) Type of Optimizers and what it does ?

16) If an user executes SELECT/INSERT/UPDATE at a time, which one is executed first.

17) Can I drop a table if a user is already running an insert/update/delete on same table?

18) How ALTER/SELECT/DROP/CREATE works -- will there be any UNDO TBS usage for DDL?

19) How do you find TOP WAIT events in Oracle ?