When this environment variable is set, calls to SYSTEM(14) will result in a 100 millisecond delay.
As per normal environment variable. The environment variable can be set dynamically with the PUTENV() function.
Looking for type ahead data using SYSTEM(14) in a tight loop can have a detrimental impact on system performance because left unchecked, such loops can consume all available system resources. With JBC_BLOCK_SYSTEM14 set, each call to SYSTEM(14) incurs a 100 millisecond delay, so a loop with SYSTEM(14) doesn't waste system resources by looping too quickly.
It should be noted that the accuracy of the pause is dependent on the granularity of the system clock and the load on the system. Most operating systems and hardware will provide a granularity of 10 milliseconds.