Codes & Concepts

DBA: The data block address

A Data Block Address (DBA) is the address of an Oracle data block for access purposes.

Start by getting the file and block number of the row. Example:

SQL> SELECT

  2    dbms_rowid.rowid_relative_fno(rowid) REL_FNO,

  3    dbms_rowid.rowid_block_number(rowid) BLOCKNO,

  4    empno, ename

  5  FROM emp WHERE empno = 7369;

   REL_FNO    BLOCKNO      EMPNO ENAME

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

         4         20       7369 SMITH

Now, convert the file and block numbers to a DBA address:

SQL> variable dba varchar2(30)

SQL> exec :dba := dbms_utility.make_data_block_address(4, 20);

PL/SQL procedure successfully completed.

SQL> print dba

DBA

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

16777236

Example:

SQL> SELECT dbms_utility.data_block_address_block(16777236) "BLOCK",

  2         dbms_utility.data_block_address_file(16777236) "FILE"

  3    FROM dual;

     BLOCK       FILE

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

        20          4