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dul without system tablespace

原创 Linux操作系统 作者:dla001 时间:2011-06-30 13:37:16 0 删除 编辑

转自:Oracle Clinic


Using DUL to Recover From Database Corruption (with some examples)

Table Of Contents
1. Introduction
2. Using DUL
  2.1 Create an appropriate init.dul file
  2.2 Create the control.dul file
  2.3 Unload the object information
  2.4 Invoke DUL
  2.5 Rebuild the database
3. How to rebuild object definitions that are stored in the data dictionary ?
4. How to unload data when the segment header block is corrupted ?
5. How to unload data when the file header block is corrupted ?
6. How to unload data without the system tablespace ?
7. Appendix A : Where to find the executables ?
8. References

1. Introduction

This document is to explain how to use DUL rather than to give a full
explanation of Bernard's Data UnLoader capabilities.

This document is for internal use only and should not be given to customers at
any time, Dul should always be used by or under the supervision of a support

DUL (Data UnLoader) is intended to retrieve data from the Oracle Database that
cannot be retrieved otherwise. This is not an alternative for the export
utility or SQL*Loader. The database may be corrupted but an individual data
block used must be 100% correct. During all unloading checks are made to make
sure that blocks are not corrupted and belong to the correct segment. If a
corrupted block is detected by DUL, an error message is printed in the loader
file and to the standard output, but this will not terminate the unloading of
the next row or block.

2. Using DUL

First you must retrieve the necessary information about the objects that exists
in the database, these statistics will be loaded into the DUL dictionary to
unload the database objects.

This information is retrieved from the USER$, OBJ$, TAB$ and COL$ tables that
were created at database creation time, they can be unloaded based on the fact
that object numbers are fixed for these tables due to the rigid nature of sql.
bsq. DUL can find the information in the system tablespace, therefor the system
tablespace datafile(s) must be included in the control file, if this datafile(s)
is not present see chapter 6.

 2.1 Create an appropriate "init.dul" file

    REM Platform. specific parameters (NT)
    REM A List of parameters for the most common platforms can be obtained from
    osd_word_size = 32

    REM Sizes of dul dictionary caches. If one of these is too low startup will
    REM fail.

    REM Location and filename of the control file, default value is control.dul
    REM in the current directory
    control_file = D:\Dul\control_orcl.dul

    REM Database blocksize, can be found in the init.ora file or can be
    REM retrieved by doing "show parameter %db_block_size%" in server manager
    REM (svrmgr23/30/l) changes this parameter to whatever the block size is of
    REM the crashed database.

    REM Can/must be specified when data is needed into export/import format.
    REM this will create a file suitable to use by the oracle import utility,
    REM although the generated file is completely different from a table mode
    REM export generated by the EXP utility. It is a single table dump file
    REM with only a create table structure statement and the table data.
    REM Grants, storage clauses, triggers are not included into this dump file !

    REM Compatible parameter must be specified an can be either 6, 7 or 8

    REM This parameter is optional and can be specified on platforms that do
    REM not support long file names (e.g. 8.3 DOS) or when the file format that
    REM DUL uses "owner_name.table_name.ext" is not acceptable. The dump files
    REM will be something like dump001.ext, dump002.ext, etc in this case.
    file = dump

   A complete list can be obtained at
   html section "DUL Parameters" although this init.dul file will work in most
   cases and contains all accurate parameters to succesfully complete the

 2.2 Create the "control.dul" file

   A good knowledge about the logical tablespace and physical datafile
   structure is needed or you can do the following queries when the database
   is mounted :

    Oracle 6, 7
    > connect internal
    > spool control.DUL
    > select * from v$dbfile;
    > spool off

    Oracle 8
    > connect internal
    > spool control.DUL
    > select ts#, rfile#, name from v$datafile;
    > spool off

   Edit the spool file and change, if needed, the datafile location and stripe
   out unnecessary information like table headers, feedback line, etc...
   A sample control file looks something like this :

    REM Oracle7 control file

    REM Oracle8 control file

  Note : Each entry can contain a part of a datafile, this can be useful when
         you need to split datafiles that are too big for DUL, so that each
         part is smaller than for example 2GB. For example :

         REM Oracle8 with a datafile split into multiple parts, each part is
         REM smaller than 1GB !
         1 2 D:\DUL\DATAFILE\USR1ORCL.DBF startblock 1 endblock 1000000
         1 2 D:\DUL\DATAFILE\USR1ORCL.DBF startblock 1000001 endblock 2000000
         1 2 D:\DUL\DATAFILE\USR1ORCL.DBF startblock 2000001 endblock 2550000

 2.3 Unload the object information

   Start the DUL utility with the appropriate ddl (Dul Description Language)
   script. There are 3 scripts available to unload the USER$, OBJ$, TAB$ and
   COL$ tables according to the database version.

   Oracle6 :> dul8.exe dictv6.ddl
   Oracle7 :> dul8.exe dictv7.ddl
   Oracle8 :> dul8.exe dictv8.ddl

   Data UnLoader: Release - Internal Use Only - on Tue Jun 22 22:19:
   Copyright (c) 1994/1999 Bernard van Duijnen All rights reserved.

   Parameter altered
   Session altered.
   Parameter altered
   Session altered.
   Parameter altered
   Session altered.
   Parameter altered
   Session altered.
   . unloading table                      OBJ$    2271 rows unloaded
   . unloading table                      TAB$     245 rows unloaded
   . unloading table                      COL$   10489 rows unloaded
   . unloading table                     USER$      22 rows unloaded
   . unloading table                  TABPART$       0 rows unloaded
   . unloading table                      IND$     274 rows unloaded
   . unloading table                     ICOL$     514 rows unloaded
   . unloading table                      LOB$      13 rows unloaded

   Life is DUL without it

   This will unload the data of the USER$, OBJ$, TAB$ and COl$ data dictionary
   tables into SQL*Loader files , this can not be manipulated into dump files
   of the import format. The parameter export_mode = false is hardcoded into
   the ddl scripts and can not be changed to the value "true" since this will
   cause DUL to fail with the error:

   . unloading table                      OBJ$
   DUL: Error: Column "DATAOBJ#" actual size(2) greater than length in column

 2.4 Invoke DUL

   Start DUL in interactive mode or you can prepare a scripts that contains all
   the ddl commands to unload the necessary data from the database. I will
   describe in this document the most used commands, this is not a complete list
   of possible parameters that can be specified. A complete list can be found at section "DDL Description".

   DUL> unload database;
     => this will unload the entire database tables(includes sys'tables as well)

   DUL> unload user ;
     => this will unload all the tables owned by that particullarly user.

   DUL> unload table ;
     => this will unload the specified table owned by that username

   DUL> describe ;
     => will represent the table columns with there relative pointers to the
        datafile(s) owned by the specified user.

   DUL> scan database;
     => Scans all blocks of all data files.
	Two files are generated:
        1: seg.dat information of found segment headers (index/cluster/table)
              (object id, file number, and block number).
         2: ext.dat information of contiguous table/cluster data blocks.
              (object id(V7), file and block number of segment header (V6),
              file number and block number of first block,
              number of blocks, number of tables)

   DUL> scan tables;
     => Uses seg.dat and ext.dat as input.
        Scans all tables in all data segments (a header block and at least one
        matching extent with at least 1 table).

 2.5 Rebuild the database

 Create the new database and use import or SQL*Loader to restore the data
 retrieved by DUL. Note that when you only unloaded the data that table
 structures, indexation, grants, PL/SQL and triggers will no longer exist in
 the new database. To obtain an exactly same copy of the database as before
 you will need to rerun your creation scripts for the tables, indexes, PL/SQL,

 If you don't have these scripts then you will need to perform. the steps
 described in section 3 of this document.

3. How to rebuild object definitions that are stored in the data dictionary

You want to rebuild PL/SQL(packages, procedures, functions or triggers), grants,
indexes, constraints or storage clauses(old table structure) with DUL. This can
be done but is a little bit tricky. You need to unload the relevant data
dictionary tables using DUL and then load these tables into a healthy database,
be sure to use a different user than sys or (system). Loading the data
dictionary tables of the crashed database into the healthy database dictionary
could corrupt the healthy database as well.

Detailed explanation to retrieve for example pl/sql packages / procedures /
functions from a corrupted database :

  1) Follow the steps explained in the "Using DUL" section and unload the data
     dictionary table "source$"

  2) Create a new user into a healthy database and specify the desired default
     and temporary tablespace.

  3) Grant connect, resource, imp_full_database to the new user.

  4) Import/load the table "source$" into the new created schema:

     e.g.: imp80 userid=newuser/passw file=d:\dul\scott_emp.dmp
           log=d:\dul\impemp.txt full=y

  5) You can now query from the table  to rebuild the pl/sql
     procedures/functions from the corrupted database. Scripts can be found on
     WebIv to generate such PL/SQL creation scripts.

The same steps can be followed to recreate indexes, constraints, and storage
parameters or to regrant privileges to the appropiate users. Please notice that
you always need to use a script. of some kind that can recreate the objects and
include all the features of the crashed database version. For example : when
the crashed database is of version 7.3.4 and you have several bitmap indexes,
if you would use a script. that supports version 7.3.2 or prior, then you won't
be able to recreate the bitmap indexes succesful !

4. How to unload data when the segment header block is corrupted

When DUL can't retrieve data block information on the normal way, it can scan
the database to create its own segment/extent map. The procedure of scanning
the database is necessary to unload the data from the datafiles.
(to illustrate this example I copied an empty block ontop of the segment header

 1) Create an appropiate "init.dul" (see 2.1) and "control.dul" (see 2.2) file.

 2) Unload the table. This will fail and indicate that there is a corruption in
    the segment header block:

    DUL> unload table scott.emp;
    . unloading table                       EMP
    DUL: Warning: Block is never used, block type is zero
    DUL: Error: While checking tablespace 6 file 10 block 2
    DUL: Error: While processing block ts#=6, file#=10, block#=2
    DUL: Error: Could not read/parse segment header
        0 rows unloaded

 3) run the scan database command :

    DUL> scan database;
     tablespace 0, data file 1: 10239 blocks scanned
     tablespace 6, data file 10: 2559 blocks scanned

 4) Indicate to DUL that it should use its own generated extent map rather than
    the segment header information.

    DUL> alter session set use_scanned_extent_map = true;
    Parameter altered
    Session altered.
    DUL> unload table scott.emp;
    . unloading table                  EMP       14 rows unloaded

5. How to unload data when the datafile header block is corrupted

A corruption in the datafile header block is always listed at the moment you
open the database this is not like a header segment block corruption (see point
4) where the database can be succesfully openend and the corruption is listed
at the moment you do a query of a table. Dul has no problems with recovering
from such situations although there are other alternatives of recovering from
this situation like patching the datafile header block.

The error you will receive looks something like :
  ORACLE instance started.
  Total System Global Area                         11739136 bytes
  Fixed Size                                          49152 bytes
  Variable Size                                     7421952 bytes
  Database Buffers                                  4194304 bytes
  Redo Buffers                                        73728 bytes
  Database mounted.
  ORA-01122: database file 10 failed verification check
  ORA-01110: data file 10: 'D:\DATA\TRGT\DATAFILES\JUR1TRGT.DBF'
  ORA-01251: Unknown File Header Version read for file number 10

6. How to unload data without the system tablespace

If datafiles are not available for the system tablespace the unload can still
continue but the object information can't be retrieved from the data dictionary
tables USER$, OBJ$, TAB$ and COL$. So ownername, tablename and columnnames will
not be loaded into the DUL dictionary. Identifying the tables can be an
overwhelming task and a good knowledge of the RDBMS internals are needed here.
First of all you need a good knowledge of your application and it's tables.
Column types can be guessed by DUL, but table and column names will be lost.

Any old system tablespace from the same database (may be weeks old) can be a
great help !

1) Create the "init.dul" file and the "control.dul" file as explained in above
   steps 1 and 2. In this case the control file will contain all the datafiles
   from which you want to restore but it doesn't require the system tablespace

2) Then You invoke dul and type the following command :

   DUL> scan database;
   data file 6 1280 blocks scanned

   This will build the extent and segment map. Probably the dul command
   interpreter will be terminated as well.

3) reinvoke the dul command interpreter and do the following :

     Data UnLoader: Release - Internal Use Only - on Tue Aug 03 13:33:

     Copyright (c) 1994/1999 Oracle Corporation, The Netherlands. All rights res
     Loaded 4 segments
     Loaded 2 extents
     Extent map sorted
     DUL> alter session set use_scanned_extent_map = true;
     DUL> scan tables; (or scan extents;)

     Scanning tables with segment header

     Oid 1078 fno 6 bno 2 table number 0

     Colno  Seen MaxIntSz Null% C75% C100 Num% NiNu% Dat% Rid%
         1     4        2    0%   0%   0% 100% 100%   0%   0%
         2     4       10    0% 100% 100% 100%   0%   0%   0%
         3     4        8    0% 100% 100% 100%   0%   0%  50%
     "20" "RESEARCH" "DALLAS"
     "30" "SALES" "CHICAGO"

     Oid 1080 fno 6 bno 12 table number 0

     Colno  Seen MaxIntSz Null% C75% C100 Num% NiNu% Dat% Rid%
         1    14        3    0%   0%   0% 100% 100%   0%   0%
         2    14        6    0% 100% 100% 100%   0%   0%  21%
         3    14        9    0% 100% 100% 100%   0%   0%   0%
         4    14        3    7%   0%   0% 100% 100%   0%   0%
         5    14        7    0%   0%   0%   0%   0% 100%   0%
         6    14        3    0%   0%   0% 100% 100%   0%   0%
         7    14        2   71%   0%   0% 100% 100%   0%   0%
         8    14        2    0%   0%   0% 100% 100%   0%   0%
     "7369" "SMITH" "CLERK" "7902" "17-DEC-1980 AD 00:00:00" "800" "" "20"
     "7499" "ALLEN" "SALESMAN" "7698" "20-FEB-1981 AD 00:00:00" "1600" "300" "30"
     "7521" "WARD" "SALESMAN" "7698" "22-FEB-1981 AD 00:00:00" "1250" "500" "30"
     "7566" "JONES" "MANAGER" "7839" "02-APR-1981 AD 00:00:00" "2975" "" "20"
     "7654" "MARTIN" "SALESMAN" "7698" "28-SEP-1981 AD 00:00:00" "1250" "1400" "30"

   Note : it might be best that you redirect the output to a logfile since
          commands like the "scan tables" can produce a lot of output.
          On Windows NT you can do the following command :
          C:\> dul8 > c:\temp\scan_tables.txt
           scan tables;

4) Identify the lost tables from the output of step 3; if you look carefully to
   the output above then you will notice that the unload syntax is already given
   but that the table name will be of the format t_0 and the column
   names will be of the format C; datatypes will not be an exact match of
   the datatype as it was before.

   Look especially for strings like "Oid 1078 fno 6 bno 2 table number 0" where:
   id = object id, will be used to unload the object
   fno = (data)file number
   bno = block number

5) Unload the identified tables with the "unload table" command :

     DUL> unload table dept (deptno number(2), dname varchar2(14),
            loc varchar2(13)) storage (OBJNO 1078)
     Unloading extent(s) of table DEPT 4 rows.

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