GENCERT gets the ACF00176 message.
Release : 16.0
Component : CA ACF2 for z/OS
Certificates are stored in the ACF2 database with a record id of logonid.suffix. The ACF00176 error message will occur if the SUBJSDN for the GENCERT of a certificate has the same SUBJSDN as an existing certificate owned by the same logonid. The SUBJSDN of a certificate should be unique within the ESM(ACF2, Top Secret, RACF) database. To correct the problem change the SUBJSDN of the certificate to be GENCERTed so the SUBJSDN is unique.