is it possible to delete/rename default accounts in oracle database?

Oracle Database installation includes several predefined user accounts.The three types of predefined accounts are:

1) Administrative accounts (SYS, SYSTEM, SYSBACKUP, SYSDG, SYSKM, SYSMAN, and DBSNMP)

SYS, SYSTEM, SYSBACKUP, SYSDG, and SYSKM are described in "About Database Administrator Security and Privileges". SYSMAN is used to perform Oracle Enterprise Manager Cloud Control administration tasks. The management agent of Cloud Control uses the DBSNMP account to monitor and manage the database. You must not delete these accounts.

2) Sample schema accounts
These accounts are used for examples in Oracle Database documentation and instructional materials. Examples are HR, SH, and OE. You must unlock these accounts and reset their passwords before using them.

3) Internal accounts.
These accounts are created so that individual Oracle Database features or components can have their own schemas. You must not delete internal accounts, and you must not attempt to log in with them.


The only users that are allowed to be dropped or altered are the sample schema accounts because these are provided just for demonstration and example purposes. Dropping them will not affect the functionality of the database.

For all the other accounts provided by default by Oracle it is not supported to drop or change their configuration. Also note that SYS and SYSTEM are the most powerful users in the database and dropping them will certainly broke the functionality of the database.

Here is a list with all the account provided by Oracle and their usage:
Predefined User Accounts Provided by Oracle Database:
https://docs.oracle.com/database/121/TDPSG/GUID-3EC7A894-D620-4497-AFB1-64EB8C33D854.htm#TDPSG20030