Installing the Oracle Database - Expert Consolidation in Oracle Database 12c - page 213

Mapping Privileged Operating System Groups
The screen shown in Figure 6-23 is one of the few really new screens when comparing Oracle 12c to 11g Release 2.
Previous releases only used the OSDBA and OSOPER groups, whereas Oracle 12c adds some new ones to worry about.
These groups allow an even finer separation of duties. Refer back to Chapter 5 for a complete discussion of their roles
and purposes.
Figure 6-23. Mapping oracle's groups to privileged groups
It is of course still possible to use the “dba” operating system group exclusively for all the different groups
available in Oracle, but doing so negates the advantages offered by the new system. I recommend the creation of the
backupdba, dgdba, and kmdba groups on the operating system, and the Oracle user should have these assigned as its
secondary groups. At the risk of repeating myself: you should create the operating system groups and map the Oracle
user to them even if you are not planning to use them straight away. Configuring the database software in the new way
gives you the flexibility of gradually adding functionality without having to reinstall the binaries. In the screen above
the Oracle user had all of the default groups assigned, and the installer picked those up.
Review your settings and click on “Next” to proceed.