SYSTIMESTAMP

This is how you extract the microseconds portion of the timestamp. It was tested on Oracle 9:

SQL> col systimestamp format a40

SQL> col microseconds format a12

SQL> select systimestamp,

  2  to_char(systimestamp,'ff') microseconds

  3  from dual

  4  /

SYSTIMESTAMP                             MICROSECONDS

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

20-JUN-12 12.17.11.790899 +01:00         790899

SQL>