There is also another view which is taken in the orgs in which I;ve worked..

a). App DBA
b). Tech DBA

a) App DBA - Handles Database Admin such as, segment craetion/monitoring/manipulation, performance montioring, user management, tablespace monitoring, some issue management. On ALL databases e.g. (Prod and Dev).

b). Tech DBA - Oracle install, instance creation, patch appliaction, backup and Recovery etc. On ALL databases e.g. (Prod and Dev).

Cheers,