You can use the CEE3SPM callable service to set or reset the exponent-underflow
mask bit in the program mask; the bit controls whether a program interruption
occurs when exponent-underflow occurs, as follows: - When the bit is on, the program interruption occurs and condition
CEE34D is signaled.
- When the bit is off, no program interruption occurs; therefore
no condition is signaled.
See z/OS Language Environment Programming Reference for
more information about the CEE3SPM callable service.