In 10g SMON gathers information on columns that are used in predicates and updates them in COL_USAGE$. Here is the column description of the table.

SQL> desc sys.col_usage$
Name Null? Type
—————————————– ——– —————————-
OBJ# – sys.obj$ -> obj#
INTCOL# – sys.col$ -> col#
EQUALITY_PREDS – Number of constant equality predicate
EQUIJOIN_PREDS – Number of equijoin of the form table1.column1 = table2.column2
NONEQUIJOIN_PREDS – Number of the form table1.column1 != table2.column2
RANGE_PREDS – Number of the form table1.column1 between value1 and value2
LIKE_PREDS – Number of times like is used
NULL_PREDS – Number of times NULL predicate is used
TIMESTAMP – Last time when it was updated