clustering factor

Clustering Factor shows how synchronized the indexes are. Clustering Factor is updated after running dbms_stats on a particular index.

A good clustering factor is when the clustering factor is near the number of blocks in the index.
A bad clustering factor is when the clustering factor is near the number of distinct rows in the index.

So for each key,
If the child records are found in the same data block then access will be quicker. Good clustering factor.

If the child records are found in may data blocks then access will be slower. bad clustering factor.

locked statistics

you can lock statistics. I'm guessing this means that the stats for this table will never change (until at least you lock them).

to lock statistics try:

dbms_stats.lock_table_stats(owner, tablename);

there should be additional parameters to lock column and index statistics as well.

Use the dba_tab_statistics view to verify what tables have been locked.