You can use ROLLBACK or ROLLFORWARD statements to recover base tables that have hash indexes defined on them; however, the hash indexes are not rebuilt during the recovery process. Instead, they are marked as not valid. You must drop and recreate any such hash indexes before the Optimizer can use them again to generate a query plan.
When a hash index has been marked not valid, the SHOW HASH INDEX statement displays a special status message to inform you that the hash index has been so marked.