User accounts can be accessed through a system view called ALL_USERS. A simple SELECT statement can be used to get a list of all user accounts. Try the following script:

>.insqlplus /nolog

SQL> connect SYSTEM/globalguideline

Connected.

SQL> SELECT * FROM ALL_USERS;

USERNAME     USER_ID CREATED

------------------------------ ---------- ---------

FLOWS_020100     35 07-FEB-06

FLOWS_FILES     34 07-FEB-06

HR       33 07-FEB-06

MDSYS      32 07-FEB-06

ANONYMOUS     28 07-FEB-06

XDB      27 07-FEB-06

CTXSYS      25 07-FEB-06

DBSNMP      23 07-FEB-06

TSMSYS      20 07-FEB-06

DIP      18 07-FEB-06

OUTLN      11 07-FEB-06

SYSTEM      5 07-FEB-06

SYS       0 07-FEB-06