Predefined and Customized Users
Although we can look up the predefined accounts in the official documentation to make sure that we won't touch them in database, it's tedious to match each of every account one by one. Therefore, we still need a faster and better way to focus these accounts.
In this post, we see two groups of accounts in the database, one is the default accounts, the other is the customized accounts. To tell the one from the other, we perform a query on DBA_USERS.
First of all, we format the date time of current session.
SQL> set pagesize 100;
SQL> column username format a25;
SQL> alter session set nls_date_format='yyyy-mm-dd hh24:mi:ss';
Session altered.
Then perform the query.
SQL> select username, created from dba_users order by 2;
The returned result can be categorized as two groups by their creation date, one is the default accounts who are created very early, the other is the customized users who are created later.
1. Default Accounts
Since we ordered the result by CREATED date, the predefined accounts come first.
USERNAME CREATED
------------------------- -------------------
SYS 2019-04-17 00:56:32
SYSTEM 2019-04-17 00:56:33
SYSDG 2019-04-17 00:56:33
SYSKM 2019-04-17 00:56:33
AUDSYS 2019-04-17 00:56:33
SYSRAC 2019-04-17 00:56:33
SYSBACKUP 2019-04-17 00:56:33
OUTLN 2019-04-17 00:56:39
GSMUSER 2019-04-17 01:21:29
GSMADMIN_INTERNAL 2019-04-17 01:21:29
DIP 2019-04-17 01:21:39
XS$NULL 2019-04-17 01:22:12
DBSFWUSER 2019-04-17 01:22:26
REMOTE_SCHEDULER_AGENT 2019-04-17 01:22:26
ORACLE_OCM 2019-04-17 01:23:29
SYS$UMF 2019-04-17 01:29:33
DBSNMP 2019-04-17 01:32:53
APPQOSSYS 2019-04-17 01:32:55
GSMCATUSER 2019-04-17 01:33:01
GGSYS 2019-04-17 01:33:05
XDB 2019-04-17 01:34:52
ANONYMOUS 2019-04-17 01:34:52
WMSYS 2019-04-17 01:40:46
OJVMSYS 2019-04-17 01:43:54
CTXSYS 2019-04-17 01:47:29
ORDDATA 2019-04-17 01:48:40
SI_INFORMTN_SCHEMA 2019-04-17 01:48:40
ORDPLUGINS 2019-04-17 01:48:40
ORDSYS 2019-04-17 01:48:40
MDSYS 2019-04-17 01:48:40
OLAPSYS 2019-04-17 01:53:19
MDDATA 2019-04-17 01:58:11
LBACSYS 2019-04-17 02:02:26
DVF 2019-04-17 02:03:13
DVSYS 2019-04-17 02:03:13
As you can see, they are created in 2019.
2. Customized Accounts
The second group are distinctively created in 2020, who are the customized users.
PDBADMIN 2020-07-14 23:22:48
HR 2020-07-20 23:33:02
OE 2020-07-20 23:33:07
PM 2020-07-20 23:33:52
IX 2020-07-20 23:33:58
SH 2020-07-20 23:34:05
BI 2020-07-20 23:34:54
42 rows selected.
That's how we identify who are the default and who are not the default users.
In a multitenant environment, PDBADMIN is created by the database system once the PDB has been created, who is not a really required account.