This document gives more details behind what LU00042 does.
Release : 19.0
Component : CA IDMS/DB
IDMS has some routines executed at startup which are designed to handle the very unlikely event that it encounters any z/OS CSA storage corruption.
It attempts to either repair or free any corrupted storage chains.
There was a bug in this code which could cause a loop.
LU00042 fixes that bug.