Doc ID:  Note:35512.1 
Subject:  DBVERIFY - Database file Verification Utility (7.3.2 onwards) 
Type:  REFERENCE 
Status:  PUBLISHED 
 Content Type:  TEXT/PLAIN 
Creation Date:  14-AUG-1997 
Last Revision Date:  29-FEB-2000 
Language:  USAENG 
 

DB Verify
~~~~~~~~~
  DB Verify is a utility supplied with Oracle releases 7.3.2 onwards. 
  It checks isolated data and index block internals for consistency and can
  be used to give some degree of confidence that a datafile is free from 
  corruptions. It performs checks at a block level and so unlike 'ANALYZE
  TABLE .. VALIDATE STRUCTURE CASCADE' it does *NOT* perform any cross checks 
  between index and data blocks.

  DBV can be used against data files from Oracle releases prior to 7.3 but it
  must be executed from the ORACLE_HOME environment in which it is supplied.
DBV the NLS code and error message files you cannot use the  executable 
stand alone.


Usage
~~~~~
  Unix:		dbv FILE [options]
	
  Windows NT:	DBVERFxx FILE [options]		(xx is the version)
						(Eg: DBVERF80 for Oracle 8.0)
  
  Options:
	Keyword   Description        (Default)
	----------------------------------------------
	FILE      File to Verify     (NONE)
	START     Start Block        (First Block of File)
	END       End Block          (Last Block of File)
	BLOCKSIZE Logical Block Size (2048)
	LOGFILE   Output Log         (NONE)
	FEEDBACK  Display Progress   (0)


Usage Notes
~~~~~~~~~~~
  1. This utility can ONLY be used against DATA files. 
     It CANNOT be used to verify redo log files nor control files.

  2. Datafiles are opened read-only.
     Hence DB Verify CAN be used against open database files where there
     are no operating system file locks.
     Note: On some platforms such as Windows NT or VMS database files
           are locked at operating system level requiring the database
           to be shut down prior to running DBV. 
           
  3. In 7.3 (on Unix) you cannot directly reference a raw device as DBV
     expects a filename extension. The workaround is to create
     a symbolic link to the raw device - the link name MUST have
     an extension.

	Eg: ln -s /dev/rdsk/mydevice /tmp/mydevice.dbf
	    Now use DBV against /tmp/mydevice.dbf 

  4. For RAW devices you should use the START and END parameters
     to avoid running off the end of the Oracle file space.
     Use: START=1 END=<num blocks -1>
     If you get the END value too high DBV can report the last
     page/s of the file as corrupt as these are beyond the 
     end of the Oracle portion of the raw device.

     The values for START and END can be found from data dictionary views. 
 
     To find value for START (First Block of File)for file_id=5, 
     run the query:             
     SQL> select BLOCK_ID, BLOCKS from dba_extents 
          where FILE_ID=5 order by BLOCK_ID;
    
         BLOCK_ID   BLOCKS                
         ---------- ---------------                         
            2         20 ========> this is the value for START.                   
           22          5                         
           27          5  
           32          5 

    You can find the value for END as sum of values for START and BLOCKS, 
    where:
    
    START is "First Block of File"                           
    BLOCKS is the file size expressed in Oracle blocks                            
                                                   
    You can find value for BLOCKS from v$datafile or dba_data_files views.          
                                            
    For example to find out BLOCKS for file#=5:                                                                    
    SQL> select BLOCKS from v$datafile where FILE#=5;                           
            BLOCKS                                                                         
            ----------                                                                     
              256                                                                         
                                                           

Example Results:
~~~~~~~~~~~~~~~~
	DBVERIFY - Verification starting : FILE = users01.dbf
	kdbchk: a row ends in the middle of another
	        tab=0 slot=1 begin=0x7a0 len=0x14
	Page 3 failed with check code 5
	Page 10 is marked software corrupt
	Page 12 is marked software corrupt

	DBVERIFY - Verification complete

	Total Pages Examined         : 512
	Total Pages Processed (Data) : 1
	Total Pages Failing   (Data) : 1
	Total Pages Processed (Index): 0
	Total Pages Failing   (Index): 0
	Total Pages Empty            : 507
	Total Pages Marked Corrupt   : 2
	Total Pages Influx           : 0

  If the utility reports any pages to be 'Marked Corrupt' or 'Failing' then
  re-run the command to see if the problem is transient or not. If there
  are still corruptions reported then contact your local support centre
  for advice.

 Notes:	
  1. Failing blocks are not dumped symbolically. Only the error is reported.

  2. The Page number is the database block number within the file.

  3. 'marked software corrupt' actually means the block wrapper is incorrect. 
	   This may be soft corrupt, or a completely corrupted 
	   DBA, Inc, Seq etc.. As this is not dumped you cannot tell anything
	   about the database block. See 'bchk' [NOTE:33493.1].


References:
  DBVERIFY  START and END parameters	[PR:1029262.6]