Summary

Important Observations

• GROUP_BY commands simplify your code and simplify maintenance.

• Check I/O status after performing database operations to ensure necessary conditions are highlighted. IF_STATUS supports, *OKAY, *ERROR, *VALERROR, *NORECORD, *ENDFILE, *BEGINFILE, *EQUALKEY, *NOTEQUALKEY.

• A basic Server Module component can be generated, supporting all I/O operations to the table and its indexes. You can extend this server module.

• Server Modules may be executed by a web page component, synchronously or asynchronously.

• The web page should process after executing a srvroutine asynchronously, in a Completed event handling routine for the srvroutine.

Tips and Techniques

• The CHECK_ONLY parameter on an I/O command allows you to check what would happen if the operation was performed. For example CHECK_ONLY(*yes) on a Delete command checks what would happen if the record was deleted, without actually performing the delete.

• The ISSUE_MSG parameter on the FETCH command displays a message if a record is not found. It is generally better to check using IF_STATUS and issue a more user friendly message.

• Typically, you do not need to open or close tables in LANSA applications. For performance reasons, OPEN and CLOSE commands enable this to be done.

• Special values for the Fields() parameter can be used with database commands such as FETCH, INSERT and UPDATE. For example, the following can be used with the FETCH command:

• *ALL specifies that all fields from the currently active table be fetched.

• *ALL_REAL specifies that all real fields from the currently active table be fetched.

• *ALL_VIRT specifies that all virtual fields from the currently active table be fetched.

• *EXCLUDING specifies that fields following this special value must be excluded from the field list.

• *INCLUDING specifies that fields following this special value must be included in the field list. This special value is only required after an *EXCLUDING entry has caused the field list to be in exclusion mode.

• It is strongly recommended that special values *ALL, *ALL_REAL and *ALL_VIRT are used only when really required. Fetching fields which are not needed causes the application to retrieve and map fields unnecessarily and invalidates cross-reference details (i.e. shows fields that are not used in the component).

What You Should Know

• How to use the FETCH, INSERT, UPDATE and DELETE database commands.

• How to handle errors using the IF_STATUS command when performing database table operations.

• How to use the MessageBox component to provide a confirm dialog.