If an alias index entry references the incorrect user or group, you can correct the index by altering the incorrect profile that references the given alias entry, altering it again to reference another alias entry, and finally altering the desired profile to reference the given alias entry. For example, if the alias index entry for UID 1 references MYID rather than the desired YOURID:

ALTUSER MYID OMVS(UID(1))
ALTUSER MYID OMVS(UID(2))
ALTUSER YOURID OMVS(UID(1))