There are some design tips that you can apply when designing SQL
applications to maximize your database performance.
Use live data
The term live data refers to the type of access
that the database manager uses when it retrieves data without making a copy
of the data. Using this type of access, the data, which is returned to the
program, always reflects the current values of the data in the database. The
programmer can control whether the database manager uses a copy of the data
or retrieves the data directly. This is done by specifying the allow copy
data (ALWCPYDTA) parameter on the precompiler commands or on the Start
SQL (STRSQL) command.
Reduce the number of open operations
The SQL data manipulation language statements must do database open operations in order to create an open data path (ODP) to the data. An open data path is the path through which all input/output operations for the table are performed. In a sense, it connects the SQL application to a table. The number of open operations in a program can significantly affect performance.