1. De normalizes your tables where required.
2. Proper use of index columns: An index based on numeric parts is more efficient than an index based on character columns.
3. Replace the number of columns that build up a composite key.
4. Proper partitioning of tablespaces and makes a special tablespace for special data types like CLOB, BLOB etc.
5. Data access performance can be tuned by using stored procedures or macros to crunch data in the database server to replace the network overhead and also caching data within your application to reduce the number of accesses.