Designing Interactive Panels (Panel Services) › Handle Errors › Internal Validation › Automatic Internal Validation

Automatic Internal Validation

An input error detected by internal validation where &CONTROL PANELRC is not in effect, is automatically handled by Panel Services. Control is not returned to the NCL procedure.

When an error is detected by internal validation, Panel Services assigns the appropriate error text to the &SYSMSG variable, automatically redisplays the panel, rings the terminal alarm, and places the cursor at the field in error. The display options defined within the #ERR statement for the panel are applied to the erroneous field (for example, color or highlighting attributes).

When designing your panel, ensure the &SYSMSG variable field is described somewhere on it:

• Position the &SYSMSG field towards the top of the panel so any message it includes is visible in split screen mode. If &SYSMSG is not provided, the error text cannot display and the operator might not be able to find the cause of error. (The error message texts used by internal validation are detailed in the #FLD control statement EDIT operand.)
• The field for the &SYSMSG variable is normally a high-intensity field, or some prominent color such as red (for color terminals).
• &SYSMSG always resets to a null value when control returns to the NCL procedure if no internal validation is performed and no errors are detected. This ensures an NCL procedure does not have to explicitly clear the &SYSMSG variable if no error is found.

The &SYSMSG variable is not limited to internal validation uses. NCL procedures can use it to display error messages or text assigned during processing.

Internal validation facilities cannot address all of the validation requirements a procedure needs to perform. Like other user variables, the &SYSMSG variable does not span different nesting levels; it is unique to each level unless made available using the &CONTROL SHRVARS option.

Note: Assigning multiple word error text to the &SYSMSG variable requires that you use the NCL &STR or &ASISTR function. For example:

&SYSMSG = &STR INVALID SERIAL NUMBER
&SYSMSG = &ASISTR RESOURCE NOT ACTIVE