I tested this on Oracle 11.2. If you update a table in SQL*Plus then update it again with a different value in a PL/SQL block, the second update replaces the first:
SQL> create table tab1 as
2 select 1 col1 from dual
SQL> update tab1 set col1 = 2
1 row updated.
I saw that the SYSTEM tablespace in an Oracle 11.2 database was getting quite big so I checked the size of SYS.AUD$:
C:\Users\AJ0294094>sqlplus / as sysdba
SQL*Plus: Release 220.127.116.11.0 Production on Fri May 16 13:20:54 2014
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Oracle Database 11g Enterprise Edition Release 18.104.22.168.0 - 64bit Production
I noticed this in an Oracle 22.214.171.124.0 database. DBMS_STATS failed with an ORA-00600 and the first argument was . On investigation, it seemed to have something to do with the fact that the table had a function based index:
SQL> SELECT COUNT(*) FROM DBA_INDEXES