RMAN reports corrupted blocks after migration

After database migration from 7.3.4 to 8.1.7 RMAN may report block corruption in number of
segments (when using logical check in the backup script) but in fact there isn't corruption.

If index blocks are reported corrupted you can check it by running:

ANALYZE INDEX index_name VALIDATE STRUCTURE;

or if you cannot afford locking the table simply do a full index scan and see if it reports
any errors:

SELECT /*+ INDEX(table_name index_name) */ indexed_col1, indexed_col2 
FROM table_name;