General Db2® for i performance considerations

As you code your applications, there are some general tips that can help you optimize performance.

Effects on database performance when using long object names
Long object names are converted internally to system object names when used in SQL statements. This conversion can have some performance impacts. Names of tables, views, indexes, and aliases that are 30 characters or less will generally perform much better names longer than 30 characters.
Effects of precompile options on database performance
Several precompile options are available for creating SQL programs with improved performance. They are only options because using them could impact the function of the application. For this reason, the default value for these parameters is the value that ensures successful migration of applications from prior releases. However, you can improve performance by specifying other options.
Effects of the ALWCPYDTA parameter on database performance
Some complex queries can perform better by using a sort or hashing method to evaluate the query instead of using or creating an index.
Tips for using VARCHAR and VARGRAPHIC data types in databases
Variable-length column (VARCHAR or VARGRAPHIC) support allows you to define any number of columns in a table as variable length. If you use VARCHAR or VARGRAPHIC support, the size of a table can typically be reduced.
Using field procedures to provide column level encryption
Field procedures can provide column level encryption in DB2 for i.

Parent topic: Database performance and query optimization