4.3.3 Logical File Considerations
When planning for the use of logical files in your application database, there are a number of important considerations to make.
- Always be sure that the database architect fully understands performance issues of the DBMS which will be deployed when creating logical files. For example, on the IBM i, the use of immediate access path maintenance has performance implications when an IPL is performed or when saving objects.
- Also on the IBM i, LANSA supports the use of OPNQRYF. OPNQRYF provides extremely powerful and flexible methods of creating dynamic views over files.
- In general, it is a good practice to limit the number of logical views you create. Logical views should reflect frequently used access techniques for the files.
- RDML has many powerful file access techniques which can reduce the need for logical files. Be sure to review the capabilities of the RDML commands as part of your database design and requirements assessment.
- For RDMLX Files, the use of Select/Omit Criteria is not recommended. Instead, use the WHERE parameter to limit the data retrieved.