The VTOC index is disabled by zeroing the index bit in the format-4 DSCB and setting the bit in the first high-level VIER that indicates an invalid VTOC index structure. A system dump is written to the SYS1.DUMPxx data set, and an entry is made in the logrec data set. The VTOC is converted to nonindexed format when DADSM next allocates space on the volume. The message IEC604I (which indicates that the VTOC convert routines have been used) will be issued later.