How to reset lost or unknown Directory Manager password

Issue

The Directory Manager is the privileged database administrator, comparable to the root user in Linux. The Directory Manager entry and the corresponding password are set during the instance installation.

This password can be changed when the Directory server is online using dsconf tool as described in Changing the Directory Manager Password
however this requires the server administrator to know the current password which is not always the case.

The password can also be reset by editing the Directory server dse.ldif configuration file as described in Resetting the Directory Manager Password but this requires taking the Directory server offline in order to perform the password reset which is not always desirable.