histogram oddity: Height-balanced histograms where NDV < num_buckets

Oracle 10.2.0.2, Solaris 8

Wondering if anyone could explain this. We have 105 SYS-owned tables where num_distinct < num_buckets according to dba_tab_col_statistics (see following query). Even weirder, some columns have 217 buckets for only 1 distinct value (verified in dba_tab_histograms). What kind of sense does that make? Similarly, we have one application partition that exhibits the same symptom.

select distinct table_name, column_name, num_distinct, num_buckets from dba_tab_col_statistics where histogram = 'HEIGHT BALANCED' and num_distinct < num_buckets
order by num_distinct,num_buckets
/

-mystified

-- 
Charles Schultz

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