Most shops that are moving from record level access (RLA) to SQL data access still have logical files built using DDS that have select/omit logic (SOL) in them. This is a problem in 2 ways, first the SQL Query Engine (SQE) cannot process SOL logical files by design and forces the SQL to be executed by the Classic Query engine (CQE). This can be averted by changing the QAQQINI file so that SOL logical files are ignored. To do this, change the value of IGNORE_DERIVED_INDEXES to *YES. This is going to vastly improve your overall SQL performance considerably. (source: LinkedIn AS/400 Professionals)