CallbackArea (MQPTR)

This is a field that is available for the callback function to use.

The queue manager makes no decisions based on the contents of this field and it is passed unchanged from the CallbackArea (MQPTR) field in the MQCBC structure, which is a parameter on the callback function declaration.

The value is used only on an Operation having a value MQOP_REGISTER, with no currently defined callback, it does not replace a previous definition.

This is an input and output field to the callback function. The initial value of this field is a null pointer or null bytes.