Check the return codes for all HLLAPI function calls as a prerequisite for continuing your program. Return codes provide the following types of information:
A 3270 terminal emulation session is allowed to end while your program is running. This action can cause HLLAPI to return a system error. Your program can recover by calling the RESET SYSTEM (21) function. This function allows HLLAPI to reinitialize to its starting state.
The following standard return codes are used by most of the functions. However, these standard return codes can have slightly different interpretations when used with individual functions. The return codes that are specific to individual functions are discussed only in the individual function description. Refer to each individual function for a complete explanation of its return codes.
The following standard return codes are explained so that you can use a common error-handling routine in your HLLAPI program.
| Standard Return Codes | |
| Return Code | Explanation |
| 0 | Either the function was successfully executed, or there were no host updates since the last call was issued. |
| 1 | Either the presentation space short session ID was invalid, or the application is not connected. |
| 2 | A parameter error occurred. |
| 4 | The execution of the function was inhibited because the target presentation space was busy. For example, X or XSYSTEM is displayed in the OIA for the 3270 terminal emulation. |
| 5 | The execution of the function was inhibited for some reason other than the reasons stated in return code 4. |
| 6 | A data error occurred due to specification of an invalid parameter (for example, a length error causing truncation). |
| 7 | The specified presentation space position was invalid. |
| 8 | No prerequisite function was issued. |
| 9 | A system error occurred. |
| 10 | The function number is not supported by the emulation program. |
| 11 | The resource that you requested is unavailable (for example, too many attempts have been made to connect to the same presentation space (PS) or another application is connected to the PS). |
| 20 | Invalid keystroke caused by ESC= option. |
| 21 | OIA was updated. |
| 22 | PS was updated. |
| 23 | Both OIA and PS were updated. |
| 24 | Either the string was not found, or the presentation space is unformatted. |
| 25 | Keystrokes were not available on input queue. |
| 26 | A host event occurred. See QUERY HOST UPDATE (24) for details. |
| 28 | Field length was 0. |
| 31 | Keystroke queue overflow. Keystrokes were lost. |