When you use STEPLIB on IMS/DC online to access the Language Environment run time, any Language Environment library routines that you have preloaded will not be loaded into read-only storage. If your application has an error and overwrites non-application storage, preloaded runtime routines can become corrupted and eventually cause abends when used. At refresh time, these preloaded routines marked reentrant are not refreshed unless loaded from the LPA or the LNKLST/LPALST. Thus, the abends will recur.