statistics lock in oracle

To lock statistics for a tables:

exec dbms_stats.lock_table_stats('<schema_name>', '<tablename>');

Ex:

exec dbms_stats.lock_table_stats('scott', 'test');

when stats is locked the value of stattype_locked is ALL in dba_tab_statistics;

select owner, table_name, stattype_locked from dba_tab_statistics where stattype_locked is not null; 

To unlock table stats:

exec dbms_stats.unlock_table_stats('table_owner','table_name');

ex:

exec dbms_stats.unlock_table_stats('scott', 'test')

To lock statistics for a schema:

exec dbms_stats.lock_schema_stats('schema_owner'); 
exec dbms_stats.unlock_schema_stats('schema_owner');