Plz guide about corrupt data block in 11G

  Hello world !

   Based on some document about corrupt data block. But there is problem that I understand.

   When  use bellow script :

        select segment_name , header_file , header_block      

from dba_segments

where segment_name = 'TEST_CORRUPT'

and   owner = 'USR_CORRUPT';

  Result is:

   SEGMENT_NAME                 HEADER_FILE         HEADER_BLOCK

----------------------------        -----------                ------------

TEST_CORRUPT                     7                            130

  After that, user "dd" command in linux to made corrupt datafile at block 131 (TEST_CORRUPT reside on ts_corrupt01.dbf ):

        dd of=ts_corrupt01.dbf bs=8192 conv=notrunc seek=131 << EOF

> Make it Corrupt.

> EOF

  Is the block 130 contains some data (rows data) ? And when make corruption on 131, I can use DBMS_REPAIR. But if use: