Dynamic allocation indicates the outcome of an allocation request by a return code in general register 15 and a reason code in S99ERROR in the request block. Even when the return code indicates a successful allocation, the reason code may show that a low-level error occurred, one that was not serious enough to cause a failure. The reason code has a message associated with it, and programs that invoke dynamic allocation can process the reason code or the associated message.
Although using the message processing function is optional, failure to do so can result in difficulty diagnosing a dynamic allocation error.
This information does not describe techniques for processing the reason code; it only describes techniques for processing the message. Programs that elect to process the reason code can use IEFDB476 or DAIRFAIL to convert the reason code into the message. IEFDB476 and DAIRFAIL are IBM-supplied programs. IEFDB476 is described in Using the functions of the IEFDB476 program. DAIRFAIL is an IBM-supplied program that is described in z/OS TSO/E Programming Services.
When you want messages to be issued to the end user, it is more efficient to request it through the S99EOPTS field of the request block extension, than to convert a reason code into a message by using IEFDB476.