By the way, when you say "what is IAMUTIL" sounds strange to me - you are uisng it & you don't know what is this used for ?.. ..
The I/O measurement routine experienced an excessive number of failures when looking up data set names. Check either the system dump data sets for a dump entitled, "CA-ASTEX - DSN LOOKUP FAILED," or the logrec for S0C4 abend entries for CA-ASTEX.
If you need a better solution - please post the complete diagnostic information from the abended JOB.