The function attempts to set the time in seconds to finish a lock request and returns the previous setting. In Caché any lock request, be if a FLOCK or RLOCK, needs a specific time to timeout if lock cannot be obtained immediately. It is different than DBFCDX where attempt to lock a record returns immediately with success or failure flag.
By default this value is set to 2 seconds. You may experiment with larger/shorter period if you experience some weired behavior. In my in-production application this amount of time seems to be sufficient.