Hi I'm Oscar

I 've got a problem very serious problem I can't create an index using indextype ctxsys.context

this is my program :

create index myindex on published(dok)
indextype is ctxsys.context;

and my error is :

create index myindex on published(dok)
*
ERROR at line 1:
ORA-29855: error occurred in the execution of ODCIINDEXCREATE routine
ORA-20000: Oracle Text error:
DRG-50857: oracle error in drixtab.create_index_tables
ORA-00955: name is already used by an existing object
ORA-06512: at "CTXSYS.DRUE", line 157
ORA-06512: at "CTXSYS.TEXTINDEXMETHODS", line 186

but it's not just my first time I got this error when I try to create preference,I've got same error

this is my program :

begin
ctx_ddl.create_preference('my_multi','MULTI_COLUMN _DATASTORE');
ctx_ddl.set_attribute('my_multi','columns','column 1,column2,column3');
end;

and this is an error :

begin
*
ERROR at line 1:
ORA-20000: Oracle Text error:
DRG-12607: only ctxsys can create MULTI_COLUMN preferences
ORA-06512: at "CTXSYS.DRUE", line 157
ORA-06512: at "CTXSYS.CTX_DDL", line 55
ORA-06512: at line 2

So I need a help because this error make my thesis can't be done well

thanx