SQL & PL/SQL

Hi!

I have the following problem:

I want to drop extended stats and i get the following error:

SQL> begin
2 dbms_stats.drop_extended_stats (
3 ownname => 'ORAP'
4 ,tabname => 'TDORGEH'
5 ,extension => '(O2_KOE||''*'')'
6 );
7 end;
8 /
begin
*
FEHLER in Zeile 1:
ORA-00001: Unique Constraint (SYS.I_WRI$_OPTSTAT_HH_OBJ_ICOL_ST) verletzt
ORA-06512: in "SYS.DBMS_STATS", Zeile 8443
ORA-06512: in "SYS.DBMS_STATS", Zeile 8497
ORA-06512: in "SYS.DBMS_STATS", Zeile 31747
ORA-06512: in Zeile 2

SQL> SELECT extension_name, extension
2 FROM dba_stat_extensions
3 WHERE table_name = 'TDORGEH';

EXTENSION_NAME EXTENSION
------------------------------ -----------------------
SYS_STUU82KTNIFD_P94KDKJ9#0$08 ("O2_KOE"||'*')
SYS_STUH6U9E_VV_9BVM9I3NNRX#8S ("O3_KOE"||'*')
SYS_STUCUZFT$CCNA7ZD6R08R3T660 ("O4_KOE"||'*')
SYS_STUCSINP1TWGAB#R_V3$XR72E7 ("O5_KOE"||'*')
SYS_STUFD58RVB7F0J1IOL2Q#Z$_VB ("O6_KOE"||'*')
SYS_STU#84ID#J#21ML9$7ZN#HQ7$Q ("O7_KOE"||'*')
SYS_STUCMDCY97QZOEH7TEIAB43GUX ("O8_KOE"||'*')
SYS_STUL3EYD$4V756XR5TCCV7KP94 ("O9_KOE"||'*')
SYS_STUWBXP9BM7ZXAR$JL9C6XVT7B ("O10_KOE"||'*')

9 Zeilen ausgewõhlt.

What is the problem?