If the SET SMF or SETSMF command changes the interval value, then the current interval ends immediately and the new interval takes effect. If interval recording is not active when a job starts, there is no interval recording for that job. If interval recording is turned off and then back on with a SET command, interval recording for a job starts at the new value, at the beginning of the next job step.
If either INTVAL or SYNCVAL are changed, then the system reschedules the SMF global recording interval at that time.