It is possible to recover corrupted blocks using RMAN backups.
Here’s the situation: a user connected to SQLPlus gets a data block corruption error when queries a table.
Here’s a part of the session transcript:

SQL> connect testuser/testpassword
Connected.
SQL> select count(*) from test_table;
select count(*) from test_table
*
ERROR at line 1:

ORA-01578: ORACLE data block corrupted (file # 4, block # 2015)
ORA-01110: data file 4: ‘D:\ORACLE_DATA\DATAFILES\ORCL\USERS01.DBF’

Since we know the file and block number, we can perform block level recovery using RMAN. This is best illustrated by example:

C:\>rman target /

Recovery Manager: Release 9.2.0.4.0 – Production

Copyright (c) 1995, 2002, Oracle Corporation. All rights reserved.

connected to target database: ORCL (DBID=1507972899)

–restore AND recover specific block

RMAN> blockrecover datafile 4 block 2015;

Starting blockrecover at 26/JAN/05
using target database controlfile instead of recovery catalog
allocated channel: ORA_DISK_1
channel ORA_DISK_1: sid=19 devtype=DISK
allocated channel: ORA_DISK_2
channel ORA_DISK_2: sid=20 devtype=DISK

channel ORA_DISK_1: restoring block(s)
channel ORA_DISK_1: specifying block(s) to restore from backup set
restoring blocks of datafile 00004
channel ORA_DISK_1: restored block(s) from backup piece 1
piece handle=E:\BACKUP\0QGB0UEC_1_1.BAK tag=TAG20050124T152708 params=NULL
channel ORA_DISK_1: block restore complete

starting media recovery
media recovery complete

Finished blockrecover at 26/JAN/05

RMAN>

Now our user should be able to query the table from her SQLPlus session. Here’s her session transcript after block recovery.

SQL> select count(*) from test_table;

COUNT(*)
———-
217001

SQL>

A couple of important points regarding block recovery:

Block recovery can only be done using RMAN.
The entire database can be open while performing block recovery.
Check all database files for corruption. This is important – there could be other corrupted blocks.
Verification of database files can be done using RMAN or the dbverify utility.
To verify using RMAN simply do a complete database backup with default settings.
If RMAN detects block corruption, it will exit with an error message pointing out the guilty file/block.