Corruption in block

Full details of using DBMS_REPAIR for this can be found in the
documentation but in summary the steps are:

- Use DBMS_REPAIR.ADMIN_TABLES to create the admin tables
- Use DBMS_REPAIR.CHECK_OBJECT to find problem blocks
- Get any good data out of problem blocks before corrupting them.
- Use DBMS_REPAIR.FIX_CORRUPT_BLOCKS to mark the found problem
blocks as corrupt so that they will then signal ORA-1578
- If required use DBMS_REPAIR.SKIP_CORRUPT_BLOCKS to skip corrupt
blocks on the table.