Tyring to get a better understanding of ORACLE admin accounts In reviewing some configuration information for an ORACLE 12C server, I see that the only user assigned the DBA role appears to be SYS account. Also, the only user shown with SYSDBA and SYSOPER privileges appears to be SYS account. My understanding is that these are built in accounts that can perform all administrative functions. Absent other user accounts,  it seems to indicate that the SYS account is used to perform day to days admin functions. Shouldn't there be a "named" user with appropriately assigned privileges,versus using the SYS account?
Yes, there should be. Even the documentation mentions that:

Administrative User Accounts


  Create at least one additional administrative user and grant to that
  user an appropriate administrative role to use when performing daily
  administrative tasks. Do not use SYS and SYSTEM for these purposes.


But the database can not force you to do this. It is a discipline that some companies follow, while other companies ignore.