dbms_stats.gather_schema_stats for XDB schema

Hi ,

we scheduled a nightly Job, to gather statistics for some schemas in the Prod-DB.

some times we get error, when this job is running for XDB schema.

begin

dbms_stats.gather_schema_stats             (  ownname          => 'XDB'

                                                                      method_opt      => 'FOR ALL COLUMNS SIZE AUTO',

                                                                      options              => 'GATHER AUTO');

end;

/

ORA-20000: Insufficient privileges to analyze an object in Schema

ORA-06512: at "SYS.DBMS_STATS", line 25335

ORA-06512: at "SYS.DBMS_STATS", line 25414

ORA-06512: at "SYS.DBMS_STATS", line 25367

but sometimes it succeeded !!

this happens only on XDB.

do u have an explain for that ?

is there an exception for XDB schema !