Food for thought - Who Should Tune SQL - DBA or Developer? 

Dangerous Belief #1: DBAs bear chief responsibility for the performance of SQL statements.

Dangerous Belief #2: Applications should be designed without reference to the way data is stored, e.g., index organized tables, hash clusters, partitions, etc.

Dangerous Belief #3: Application programmers should not tailor their SQL statements to make use of existing indexes. DBAs should instead create traps to catch badly performing SQL at runtime and create new indexes as necessary to make them perform better.

Dangerous Belief #4: It is not necessary to review the Query Execution Plan of an SQL statement before releasing it into a production environment. It is further not necessary to freeze the Query Execution Plan of an SQL statement before releasing it into a production environment. It is desirable that Query Execution Plans change in response to changes in the statistical information that the query optimizer relies upon. Such changes are always for the better.

Dangerous Belief #5: The most common cause of poorly performing SQL is the failure of the DBA to collect statistical information on the distribution of data for the use of the query optimizer. This statistical information should be refreshed frequently.