Table of contents

DUL's PRINCIPLES and FEATURE LIST

STANDALONE C-PROGRAM

DUL is a standalone C program that directly retrieves rows from tables in data files. The Oracle RDBMS software is NOT used at all. DUL does dirty reads, it assumes that every transaction is committed. Nor does it check/require that media recovery has been done.

LAST RESORT

DUL is intended to retrieve data that cannot be retrieved otherwise. It is NOT an alternative for EXP, SQL*Plus etc. It is meant to be a last resort, not for normal production usage.

Before you use DUL you must be aware that the rdbms has many hidden features to force a bad database open. Undocumented init.ora parameters and events can be used to skip roll forward, to disable rollback and more.

DATABASE CORRUPT - BLOCKS OK

The database can 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 during a scan a bad block is encountered, an error message is printed in the loader file and to standard output. Unloading will continue with the next row or block.

ROWS in CLUSTERS/TABLES/INDEXES

DUL can and will only unload table/cluster data. It will NOT dump triggers, stored procedures nor create scripts for tables or views. (But the data dictionary tables describing them can be unloaded). The data will be unloaded in a format suitable for SQL*Loader or IMP. A matching control file for SQL*Loader is generated as well.

DUL8 can unload indices and index organized tables. Index unload is usefull to determine how many rows a table should have or to identify the missing rows.

CROSS PLATFORM UNLOADING

Cross-platform unloading is supported. The database can be copied from a different operating system than the DUL-host. (Databases/systems done so far: Sequent/ptx, Vax Vms, Alpha Vms, MVS, HP9000/8xx, IBM AIX, SCO Unix, Alpha OSF/1, Intel Windows NT).

The configuration parameters within "init.dul" will have to be modified to match those of the original platform and O/S rather than the platform from which the unload is being done.

ROBUST

DUL will not dump, spin or hang no matter how badly corrupted the database is.

(NEARLY) ALL ORACLE FEATURES SUPPORTED

Full support for all database constructs: row chaining, row migration, hash/index clusters, longs, raws, rowids, dates, numbers, multiple free list groups, segment high water mark, NULLS, trailing NULL columns, and unlimited extents, new block layout of Oracle8, partitioned tables, Index Organized Tables and LOBS.

SUPPORTED RDBMS VERSIONS

DUL should work with all versions 6,7, 8 and 8i. DUL has been tested with versions from 6.0.26 up to 7.3.2 and 8.1.7. Even the old block header layout (pre 6.0.27.2) is supported.

MULTI BYTE SUPPORT

DUL is essentially a single byte application. The command parser does not understand multi byte characters, but it is possible to unload any multi byte database. For all possible caveats there is a work around.

RESTRICTIONS

MLSLABELS

Multi Level Security Lables of trusted oracle are not supported.

(LONG) RAW

DUL can unload (long) raws, but there is no way to reload these 1-to-1 with SQL*Loader. There is no suitable format in SQL*Loader to preserve all long raws. Use the export mode instead or write a Pro*C program to load the data.

ORACLE8 OBJECT OPTION AND LOBS

Varrays, objects, and nested tables are not yet supported

PORTABLE

DUL can be ported to any operating system with an ANSI-C compiler. DUL has been ported to many UNIX variants, VMS and WindowsNT.

RDBMS INTERNALS

A good knowledge of the Oracle RDBMS internals is a pre requisite to be able to use DUL successfully. Andre Bakker's two days internals course is a minimum.

 

SETTING UP and USING DUL

CONFIGURATION FILES

There are two configuration files for DUL. "init.dul" contains all configuration parameters. (size of caches, details of header layout, oracle block size, output file format) In the control file, "control.dul", the data file names and the oracle file numbers must be specified.

DATA DICTIONARY AVAILABLE

The Oracle data dictionary is available if the data files which made up the SYSTEM TableSpace are available and useable. The number which Oracle assigned to these files and the name you have given them, which does not have to be the original name which Oracle knew, must be included in the "control.dul" file. You also need to eventually include the file numbers and names of any files from other TableSpaces for which you wish to eventually unload TABLES and their data. The lack of inclusion of these files will not affect the data dictionary unload step but it will affect later TABLE unloading.

USING DUL WHEN USER$, OBJ$, TAB$ and COL$ CAN BE  UNLOADED

Steps to follow:

  1. configure DUL for the target database. This means creating a correct init.dul and control.dul. The SYSTEM TableSpace's data file numbers and names must be included within the control.dul file along with any data files for TableSpaces from which you wish to unload TABLEs and their data. For Oracle8 the tablespace number and the relative file number must be specified for each datafile.
  2. Unload the (first) four data dictionary tables. Use "dul dictv7.ddl" for Oracle7 or "dul dictv6.ddl" for version 6 of Oracle. Oracle8 requires "dictv8" "dictv8" will fail for a database that has been migrated from oracle7 to oracle8 or higher. In this case you need to follow the generic bootstrap procedure
  3. Re-start DUL and unload the tables for which data files have been included within the "control.dul" file. Use one of the following commands:

Migrated database

A database that has been migrated from Oracle7 to Oracle has a different data dictionary. Be aware that it is very possible that the seed database used for Rapid Install (or one hour install) for apps database has been migrated. So even a seemingly brand new database could be in fact migrated. That is the tables are the same but they are difficult to find for DUL, because they are not in the usual place, and have different object ids. A sure sign of a migrated database is that the file number of the first system datafile is not 1 but 4 or another power of 2. (Due to the file bit layout change for oracle 8) The solution is the generic bootstrap procedure that follows the way the rdbms starts in more detail.

Generic Bootstrap Procedure

There is a new generic bootstrap procedure. The old dict.dll scripts are still supplied as a handy shortcut. If they fail you should use the complete procedure.

NO DATA DICTIONARY AVAILABLE

If data files are not available for the SYSTEM TableSpace the unload can still continue but USER, TABLE and COLUM names will not be known. Identifying the tables can be an overwhelming task. But it can be (and has been) done. You need in depth knowledge about your application and the application tables. Column types can be guessed by DUL, but table and column names are unknown. Any old SYSTEM tablespace from the same database but weeks old can be of great help!. The information that DUL uses does not change.

USING DUL WITHOUT SYSTEM TABLESPACE

Steps to follow:

  1. configure DUL for the target database. This means creating a correct init.dul and control.dul. (See Port specific parameters ). In this case control.dul file will need the numbers and names of datafiles from which TABLEs and data will be unloaded but it does not require the SYSTEM TableSpace's information.
  2. SCAN DATABASE; : scan the database, build extent and segment map
  3. SCAN TABLES; or SCAN EXTENTS; : gather row statistics
  4. Identify the lost tables from the output of step 3.
  5. UNLOAD the identified tables.
AUTOMATED SEARCH

To ease the hunt for the lost tables: the scanned statistical information in seen_tab.dat and seen_col.dat can be loaded into a fresh database. If you recreate the tables ( Hopefully the create table scripts are still available) then structure information of a "lost" table can be matched to the "seen" tables scanned information with two SQL*Plus scripts. (fill.sql and getlost.sql).

HINTS WHEN LOOKING FOR TABLES:

DDL (DUL Description Language) UNLOAD STATEMENT OVERVIEW

DUL uses an SQL like command interface. There are DDL statements to unload extents, tables, users or the entire database. Data dictionary information required can be specified in the ddl statements or taken from the previously unloaded data dictionary. The following three statements will unload the DEPT table. The most common form is if the data dictionary and the extent map are available:

         UNLOAD TABLE scott.dept;

All relevant information can be specified in the statement as well:

        REM Columns with type in the correct order
        REM The segment header loaction in the storage clause
        UNLOAD TABLE dept( deptno NUMBER, dname CHAR, loc CHAR)
               STORAGE( EXTENTS ( FILE 1 BLOCK 1205 ));

Oracle version 6:

        REM version 6 data blocks have segment header location in each block
        ALTER SESSION SET USE_SCANNED_EXTENT_MAP = TRUE;
        UNLOAD TABLE dept( deptno NUMBER, dname CHAR, loc CHAR)
               STORAGE( EXTENTS ( FILE 1 BLOCK 1205 ));

Oracle7:

        REM Oracle7 data blocks have object id in each block

        ALTER SESSION SET USE_SCANNED_EXTENT_MAP = TRUE;
        UNLOAD TABLE dept( deptno NUMBER, dname CHAR, loc CHAR)
               STORAGE( OBJNO 1501 );

DUL'S OUTPUT FORMAT.

There are three different modes of output format.

EXPORT MODE

Export mode is a feature available only in DUL version 3 or DUL8. To enable export mode, you must set the init.dul parameter EXPORT_MODE to TRUE.

For each table a separate IMP loadable file will be generated. The generated file is completely different from a table mode export generated by EXP! The file is the minimal format that IMP can load. It is a single table dump file. With only an insert table statement and the table data. Table grants, storage clauses, or triggers will not be included. An optional create table statement is included if the COMPATIBLE parameter has been set to 6 or 7. The character set indication in the file in the generated header is V6 style. It is set to mean ASCII based characterset.

Extreme care has been taken that the dump file can always be loaded with imp. Only complete good rows are written to the dump file. For this each row is buffered. The size of this buffer can changed with the init.dul parameter BUFFER. Incomplete or bad rows are not written out.

SQL*LOADER MODES

For both SQL*Loader output formats the columns will be space separated and enclosed in double quotes. Any double quote in the data will be doubled. SQL*Loader recognizes this and will load only one. The character used to enclose the columns can be changed from double quote to any character you like with the init.dul parameter LDR_ENCLOSE_CHAR.

There are two styles of physical record organization:

Stream Mode

Nothing special is done in stream mode, a newline is printed after each record. This is a compact format and can be used if the data does not contain newline characters. To enable stream mode set LDR_PHYS_REC_SIZE = 0 in init.dul.

Fixed Physical Records

This mode is essential if the data can contain newlines. One logical record, one comlete row, can be composed of multiple physical records. The default is record length is 81, this fits nicely on the screen of a VT220. The physical record size can be specified with LDR_PHYS_REC_SIZE in init.dul.

OUTPUT FILE NAMES

The file names generated are: owner name_table name.ext. The extension is ".dmp" for IMP loadable files. ".dat" and ".ctl" are used for the SQL*Loader datafile and the control file. To prevent variable substitution and other unwanted side effects, strange characters are stripped.(Only alpha numeric and '_' are allowed).

If the FILE parameter is set the generated names will be FILEnnn.ext. This possibility is a work around if the file system does not support long enough file names.

SOME DUL INTERNALS

REQUIRED INFORMATION

To unload table data from a database block the following information must be known:

  1. Column/Cluster Information: The number and type of the columns. For char or varchar columns the maximum length as well. The number of cluster columns and the table number in the cluster. This information can be supplied in the unload statement or it can be taken from the previously unloaded USER$, OBJ$, TAB$ and COL$.
  2. Segment/Extent information: When unloading a table the extent table in the data segment header block is used to locate all data blocks. The location of this segment header block (file number and block number) is taken from the data dictionary or can be specified in the unload statement. If the segment header is not correct/available then another method must be used. DUL can build its own extent map by scanning the whole database. (in a separate run of DUL with the scan database statement.)
BINARY HEADERS

C-Structs in block headers are not copied directly, they are retrieved with specialized functions. All offsets of structure members are programmed into DUL. This approach makes it possible to cross-unload. (Unload an MVS created data file on an HP) Apart from byte order only four layout types have been found so far.

  1. Vax VMS and Netware : No alignment padding between structure members.
  2. Korean Ticom Unix machines : 16 bit alignment of structure members.
  3. MS/DOS 16 bit alignment and 16 bit wordsize.
  4. Rest of the world (Including Alpha VMS) structure member alignment on member size.
MACHINE DEPENDENCIES

Machine dependencies (of the database) are configurable with parameters:

UNLOADING THE DATA DICTIONARY

DUL can use the data dictionary of the database to be unloaded if the files for it exist and are uncorrupted. For the data dictionary to be used, internal tables must be unloaded first to external files: (USER$, OBJ$, TAB$ and COL$). Scripts are provided to assist in this task. They are "dictv6.ddl" which is to be used with Oracle version 6 databases and "dictv7.ddl" for Oracle7 databases. These scripts are different for different DUL versions and cannot be intermixed..

DDL ( DUL DESCRIPTION LANGUAGE ) SPECIFICATION

[ ALTER SESSION ] SET init.dul parameter =  value ;

COMMIT;
  commit will write the updated block to disk.
  The init.dul parameter writable_datafiles must be set to true;

DESCRIBE  owner_name  . table_name ;

DUMP [ TABLESPACE  tablespace_no ]
     [ FILE  file_no  ]
     [ BLOCK  block_no  ]
     [ LEVEL  level_no  ] ;
     sets the current block and dumps it(headers only),
     last location is remembered accross calls.

PREPARE;
     Must be done after unloading the data dictionary. It will unload
     all the lob indexes needed to unload lobs.

UNLOAD DATABASE;

UNLOAD USER user_name;

UNLOAD TABLE  [  schema_name . ]  table_name 
              [ (  column_definitions ) ]
              [  cluster_clause  ]
              [  storage_clause  ] ;

UNLOAD EXTENT  table_name 
              [ (  column_definitions  ) ]
              [ TABLESPACE  tablespace_no  ] 
              FILE  extent_start_file_number
              BLOCK extent_start_block_number 
              BLOCKS  extent_size_in oracle_blocks

UPDATE SET {ub1|ub2|ub4} @  offset  =  new_value  ;
     Updates the indicated variable at the specified offset to be changed
     in the current block in memory only. Navigate to the current block with
     dump. If you like the result, use commit to really write the change.
     For instance to fix avsp corruption in c_ts# cluster:
     dump block 1093;             # move to file 1 block 1093
     update set ub2@102 = 7478;   # avsp is of type ub2 and often at  offset 102
				  # 7478 is in this case the new value
     commit;                      # write the change to disk.

storage_clause ::=
        STORAGE ( storage_specification  [ more_storage_specs ] )

storage_specification ::=
        OBJNO object_id_number 
|       TABNO cluster_table_number
|       SEGOBJNO cluster/data_object_number       /* v7/v8 style data block id */
|       FILE  data_segment_header_file_number     /* v6 style data block id */
        BLOCK data_segment_header_block_number )   
|       any_normal_storage_specification_but_silently_ignored

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)

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).

SCAN EXTENTS;
        Uses seg.dat and ext.dat as input.
        All extents for which no corresponding segment header has been found.
        (Only useful if a tablespace is not complete, or a segment header
        is corrupt).

REM any_text_you_like_till_End_Of_Line : comment
  NOT allowed inside ddl statements. ( To avoid a two layer lexical scan).

EXIT QUIT and EOF all cause DUL to terminate.

DDL ( DUL DESCRIPTION LANGUAGE ) DESCRIPTION

Rules for UNLOAD EXTENT and UNLOAD TABLE:

Extent Map

UNLOAD TABLE requires an extent map. In 99.99% of the cases the extent map in the segment header is available. In the rare 0.01% that the segment header is lost an extent map can be build with the scan database command. The self build extent map will ONLY be used during an unload if the parameter USE_SCANNED_EXTENT_MAP is set to TRUE.

All data blocks have some ID of the segment they belong to. But there is a fundamental difference between V6 and V7. Data blocks created by Oracle version 6 have the address of the segment header block. Data blocks created by Oracle7 have the segment object id in the header.

Column Specification

The column definitions must be specified in the order the columns are stored in the segment, that is ordered by col$.segcol#. This is not necessarily the same order as the columns where specified in the create table statement. Cluster columns are moved to the front, longs to the end. Columns added to the table with alter table command, are always stored last.

Unloading a single extent

UNLOAD EXTENT can be used to unload 1 or more adjacent blocks. The extent to be unloaded must be specified with the STORAGE clause: To specify a single extent use: STORAGE ( EXTENTS( FILE fno BLOCK bno BLOCKS #blocks) ) (FILE and BLOCK specify the first block, BLOCKS the size of the extent)

DUL specific column types

There are two extra DUL specific data types:

  1. UNKNOWN: a heuristic guess will be made for each column.
  2. IGNORE: the column will be skipped as if it was not there at all.

Identifying USER$, OBJ$, TAB$ and COL$

There is a "hidden" trick with file and object numbers that is used to locate the data dictionary tables. The trick is based on the fact that object numbers are fixed for OBJ$, COL$, USER$ and TAB$ due to the rigid nature of sql.bsq. This will not be documented because I myself could not understand my first attempt to describe it.

DESCRIPTION OF SCAN COMMANDS

SCAN TABLES and SCAN EXTENTS scan for the same information and produce similar output. ALL columns of ALL rows are inspected. For each column the following statistics are gathered:

These statistics are combined and a column type is suggested. Using this suggestion five rows are unloaded to show the result. These statistics are dumped to two files (seen_tab.dat and seen_col.dat). There are SQL*Loader and SQL*Plus scripts available to automate a part of the identification process. (Currently known as the getlost option).

DESCRIBE

There is a describe command. It will show the dictionary information for the table, available in DUL's dictionary cache.

DUL STARTUP SEQUENCE

During startup DUL goes through the following steps:

DUL parameters to be specified in init.dul:

ALIGN_FILLER
OBSOLETE
Replaced by OSD_C_STRUCT_ALIGNMENT
ASCII2EBCDIC
BOOLEAN
Must (var)char fields be translated from EBCDIC to ASCII. (For unloading MVS database on a ASCII host)
BIG_ENDIAN_FLAG
OBSOLETE
Replaced by OSD_BIG_ENDIAN_FLAG
BLOCKS_TO_SKIP
OBSOLETE
BUFFER
NUMBER (bytes)
row output buffer size used in export mode only. In export mode each row is first stored in this buffer, before it is written to the dump file.
COMPATIBLE
NUMBER
Database version , valid values are 6, 7 or 8. This parameter must be specified
CONTROL_FILE
TEXT
Name of the DUL control file (default: "control.dul").
DBA_FILE_BITS
OBSOLETE
Replaced by OSD_DBA_FILE_BITS
DB_BLOCK_SIZE
NUMBER
Oracle block size in bytes (Maximal 32 K)
DB_LEADING_OFFSET
OBSOLETE
Replaced by OSD_FILE_LEADER_SIZE
DC_COLUMNS
NUMBER
DC_OBJECTS
NUMBER
DC_TABLES
NUMBER
DC_USERS
NUMBER
Sizes of dul dictionary caches. If one of these is too low startup will fail.
EXPORT_MODE
BOOLEAN
EXPort like output mode or SQL*Loader format
FILE
TEXT
Base for (dump or data) file name generation. Use this on 8.3 DOS like file systems
LDR_ENCLOSE_CHAR
TEXT
The character to enclose fields in SQL*Loader mode.
LDR_PHYS_REC_SIZE
NUMBER
Physical record size for the generated loader datafile.
LDR_PHYS_REC_SIZE = 0 No fixed records, each record is terminated with a newline.
LDR_PHYS_REC_SIZE > 2: Fixed record size.
MAX_OPEN_FILES
Maximum # files that are concurrently kept open at the OS level.
MAX_UNLOAD_BLOCKS
OBSOLETE
OSD_BIG_ENDIAN_FLAG
Byte order in machine word. Big Endian is also known as MSB first. DUL8 sets the default according to the machine it is running on. For an explanation why this is called Big Endian, you should read Gullivers Travels.
OSD_DBA_FILE_BITS
File Number Size in DBA in bits. Or to be more precise the size of the low order part of the file number.
OSD_FILE_LEADER_SIZE
bytes/blocks added before the real oracle file header block
OSD_C_STRUCT_ALIGNMENT
C Structure member alignment (0,16 or 32) Must be set to 32 for most ports
OSD_WORD_SIZE
Size of a machine word always 32, except for MS/DOS(16)
PARSE_HEX_ESCAPES
Use \\xhh hex escape sequences in strings while parsing. The default value is FALSE. If set to true then strange characters can be specified using escape sequences. This feature is also for specifying multi-byte characters.
TICOM_FILLER
OBSOLETE
The new parameter is OSD_C_STRUCT_ALIGNMENT
USE_SCANNED_EXTENT_MAP
BOOLEAN
Use the scanned extent map in ext.dat in unload table. This parameter is only useful if some segment headers are missing or incorrect.

SAMPLE init.dul :

# sample init.dul configuration parameters
# these must be big enough for the database in question
# the cache must hold all entries from the dollar tables.
dc_columns = 200000
dc_tables = 10000
dc_objects = 10000
dc_users = 40

# OS specific parameters
osd_big_endian_flag = false
osd_dba_file_bits = 6
osd_c_struct_alignment = 32
osd_file_leader_size = 1

# database parameters
db_block_size = 2048

# loader format definitions
LDR_ENCLOSE_CHAR = "
LDR_PHYS_REC_SIZE = 81

Configuring the port dependent parameters

osd_big_endian_flag

big endian or little endian (byte order in machine words): HP, SUN and mainframes are generally big endian: OSD_BIG_ENDIAN_FLAG = TRUE. DEC and Intel platforms are little endian: OSD_BIG_ENDIAN_FLAG = FALSE. The default is correct for the platform where DUL is running on.

There is no standard trick for this, the following might work on a unix system:

  echo dul | od -x
  If the output is like:
     0000000 6475 6c0a
     0000004
  You are on a big endian machine (OSD_BIG_ENDIAN_FLAG=TRUE).

  If you see:
     0000000 7564 0a6c
     0000004
  This is a little endian machine (OSD_BIG_ENDIAN_FLAG=FALSE).
osd_dba_file_bits

The number of bits in a dba used for the low order part of file number. For most platforms osd_dba_file_bits = 10 for Oracle8. To be sure perform the following query:

  SQL> select dump(chartorowid('0.0.1')) from dual;
  
  Typ=69 Len=6: 8,0,0,0,0,0    ->       osd_dba_filebits =  5 (SCO)
  Typ=69 Len=6: 4,0,0,0,0,0    ->       osd_dba_filebits =  6 (Sequent , HP)
  Typ=69 Len=6: 1,0,0,0,0,0    ->       osd_dba_filebits =  8 (NCR,AIX)
  Typ=69 Len=6: 0,16,0,0,0,0   ->       osd_dba_filebits = 12 (MVS)
  Typ=69 Len=10: 0,0,0,0,0,64,0,0,0,0      osd_dba_filebits = 10 (Oracle8)       
OSD_C_STRUCT_ALIGNMENT

Structure layout in data file headers. 0: No padding between members in a C-struct (VAX/VMS only) 16: Some korean ticom machines and MS/DOS 32: Structure members are member size aligned. (All others including ALPHA/VMS) Check the following query:

SELECT * FROM v$type_size
WHERE type IN ( 'KCBH', 'KTNO', 'KCBH', 'KTBBH', 'KTBIT', 'KDBH'
              , 'KTECT', 'KTETB', 'KTSHC') ;

In general osd_c_struct_alignment = 32 and the following output is expected:

K        KTNO     TABLE NUMBER IN CLUSTER                   1
KCB      KCBH     BLOCK COMMON HEADER                      20
KTB      KTBIT    TRANSACTION VARIABLE HEADER              24
KTB      KTBBH    TRANSACTION FIXED HEADER                 48
KDB      KDBH     DATA HEADER                              14
KTE      KTECT    EXTENT CONTROL                           44
KTE      KTETB    EXTENT TABLE                              8
KTS      KTSHC    SEGMENT HEADER                            8

8 rows selected.

For VAX/VMS and Netware ONLY osd_c_struct_alignment = 0 and this output is expected:

COMPONEN TYPE     DESCRIPTION                      SIZE
-------- -------- -------------------------------- ----------
K        KTNO     TABLE NUMBER IN CLUSTER                   1
KCB      KCBH     BLOCK COMMON HEADER                      20
KTB      KTBIT    TRANSACTION VARIABLE HEADER              23
KTB      KTBBH    TRANSACTION FIXED HEADER                 42
KDB      KDBH     DATA HEADER                              14
KTE      KTECT    EXTENT CONTROL                           39
KTE      KTETB    EXTENT TABLE                              8
KTS      KTSHC    SEGMENT HEADER                            7

8 rows selected.

If there is a different list this will require some major hacking and sniffing and possibly a major change to DUL. (Email bduijnen@nl.oracle.com)

osd_file_leader_size

Number of blocks/bytes before the oracle file header. Unix datafiles have an extra leading block ( file size, block size magic number) A large number ( > 100) is seen as a byte offset, a small number is seen as a number of oracle blocks.

Unix    :       osd_file_leader_size = 1
Vms     :       osd_file_leader_size = 0
Desktop :       osd_file_leader_size = 512
Others  :       Unknown ( Use Andre Bakker's famous PATCH utility to find out)
                An Oracle7 file header block starts with the pattern 0X0B010000.

You can add an additional byte offset in control.dul in the optional third field (for instance for AIX or DEC UNIX data files on raw device)

Control file specification

A control file (default name "control.dul") is used to translate the file numbers to file names. The format of the control has been extended:

if COMPATIBLE is 6 or 7:
  control_file_line_for_6_or_7 ::=
         file_number data_file_name
         [ optional extra leader offset ]
         [ startblock block_no ]
         [ endblock block_no ]

If COMPATIBLE is 8:
  control_file_line_for_8 ::=
          tablespace_no  relative_file_number data_file_name
         [ optional extra leader offset ]
         [ startblock block_no ]
         [ endblock block_no ]

Each entry on a separate line. The optional extra leader offset is an extra byte offset, that will be added to all lseek() operations for that datafile. This makes it possible to skip over the extra block for AIX on raw devices.

Each entry can contain a part of a datafile. This way it is possible to split datafiles that are too big for DUL in parts where each part is smaller than 2GB.

For instance:

   # AIX version 7 example with one file on raw device
   1 /usr/oracle/dbs/system.dbf
   8 /dev/rdsk/data.dbf 4096
   # Oracle8 example with a datafile split in multiple parts, each part smaller than 2GB
   0  1 /fs1/oradata/PMS/system.dbf
   1  2 /tmp/huge_file_part1 startblock 1 endblock 1000000
   1  2 /tmp/huge_file_part2 startblock 1000001 endblock 2000000
   1  2 /mnt3/huge_file_part3 startblock 2000001 endblock 2550000

The file header blocks are NOT verified. This would make it impossible to unload files with a corrupted header block. For debugging it is possible to dump the file header.

Sample unload session: data dictionary usable for DUL

  1. create a suitable "init.dul"
  2. create a control.dul
  3.     sqldba
        connect internal
        startup mount
        spool control.dul
        select * from v$dbfile;
        exit
    edit the result
    
    For Oracle8 a different query must be used:
       select ts#, rfile#, name from v$datafile;
    
  4. dul dictv7.ddl
  5. $ dul dictv7.ddl
    
    
    
    UnLoader: Version 2.0.0.0 - Very Restricted on Tue May 16 11:04:12 1995
    Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
    . unloading table                      OBJ$    1487 rows unloaded
    . unloading table                      TAB$     197 rows unloaded
    . unloading table                      COL$    5566 rows unloaded
    . unloading table                     USER$      13 rows unloaded
    
  6. restart dul
  7. UnLoader: Version 2.0.0.0 - Very Restricted on Tue May 16 11:05:00 1995
    Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
    Loaded 1487 objects
    Loaded 197 tables
    Loaded 5566 columns
    Loaded 13 users
    DUL> unload table scott.emp;
    About to unload SCOTT's tables ...
    . unloading table                       EMP      14 rows unloaded
    DUL>
    

Example unload session: data dictionary UNUSABLE for DUL

  1. create a suitable "init.dul" (See config guide)
  2. create a control.dul See above
  3. scan the database for segment headers and extents:
  4. $ dul
    UnLoader: Version 2.0.0.0 - Very Restricted on Tue May 16 11:10:16 1995
    Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
    DUL> scan database;
    data file 1 20480 blocks scanned
    data file 4 7680 blocks scanned
    data file 5 512 blocks scanned
    DUL>quit
    
  5. Restart DUL and scan the found tables for column statistics this creates a huge amount of output:
  6. echo scan tables \; | dul > scan.out&
    
    [ many lines here]
    
    
    Object id 1601 table number 0
    UNLOAD TABLE T1601_0 ( C1 NUMBER, C2 UNKNOWN, C3 UNKNOWN, C4 NUMBER, C5 DATE
            , C6 NUMBER, C7 NUMBER, C8 NUMBER )
        STORAGE ( TABNO 0 EXTENTS( FILE 1 BLOCK 10530));
    
    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%  14%   0%  21%
        3    14        9    0% 100% 100% 100%  14%   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" "-0.000025253223" "SALESMAN" "7698" "20-FEB-1981 AD 00:00:00" "1600" "30+
    
    0" "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"
    
    [ many more lines here ]
    

    This looks familiar, use the above information and your knowledge of the emp table to compose:

    UNLOAD TABLE emp ( empno number, ename char, job char, mgr number,
            hiredate date, sal number, comm number deptno number)
     STORAGE ( TABNO 0 EXTENTS( FILE 1 BLOCK 10530));
    
  7. use this statement to unload emp:
  8. $ dul
    UnLoader: Version 2.0.0.0 - Very Restricted on Tue May 16 11:46:33 1995
    Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
    Loaded 350 segments
    Loaded 204 extents
    Extent map sorted
    DUL> UNLOAD TABLE emp ( empno number, ename char, job char, mgr number,
    DUL 2> hiredate date, sal number, comm number deptno number)
    DUL 3> STORAGE ( TABNO 0 EXTENTS( FILE 1 BLOCK 10530));
    . unloading table                       EMP      14 rows unloaded
    DUL>quit
     

Example unload session: Incorrect init.dul Parameters

WRONG osd_dba_file_bits size

This can generate output similar to below. Normally this should not happen since you should create a demo database and check this via the DUL documented (in html page) query.

The mismatch in DBA's is only in the file number (first number in brackets) part. The second number, the block number, is correct.

Data UnLoader: Release 3.2.0.1 - Internal Use Only - on Wed Sep 3 10:40:33 1997
Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
Session altered.
Session altered.
Session altered.
Session altered.
Session altered.
DUL: Warning: Block[1][2] DBA in block mismatch [4][2]
DUL: Warning: Bad cache layer header file#=1, block#=2

DUL: Warning: Block[1][3] DBA in block mismatch [4][3]
DUL: Warning: Bad cache layer header file#=1, block#=3

...........and etc..........

WRONG osd_file_leader_size

This may create output similar to below, but many other flavours are possible. In this case we are a fixed number of blocks off. The file number is correct. The difference in the block numbers is constant.:

Data UnLoader: Release 3.2.0.1 - Internal Use Only - on Wed Sep 3 10:44:23 1997
Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
Session altered.
Session altered.
Session altered.
Session altered.
Session altered.

DUL: Warning: Block[1][2] DBA in block mismatch [1][3]
DUL: Warning: Bad cache layer header file#=1, block#=2

DUL: Warning: Block[1][3] DBA in block mismatch [1][4]
DUL: Warning: Bad cache layer header file#=1, block#=3

...........and etc..........

WRONG osd_c_struct_alignment

This may generate output similar to the following:

Data UnLoader: Release 3.2.0.1 - Internal Use Only - on Wed Sep 3 10:46:10 1997
Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
Session altered.
Session altered.
Session altered.
Session altered.
Session altered.
. unloading table OBJ$

DUL: Warning: file# 0 is out of range
DUL: Warning: Cannot read data block file#=0, block# = 262145
OS error 2: No such file or directory

DUL: Warning: file# 0 is out of range
DUL: Warning: Cannot read data block file#=0, block# = 262146
OS error 2: No such file or directory

...........and etc..........

WRONG db_block_size

The following output was generated when the db_block_size was set too small. The correct value was 4096 and it was set to 2048. Normally, the value for this parameter should be taken from the Oracle instances's init.ora file and will not be correctly set.

Data UnLoader: Release 3.2.0.1 - Internal Use Only - on Thu Sep 4 12:38:25 1997
Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
Session altered.
Session altered.
Session altered.
Session altered.
Session altered.
DUL: Warning: Block[1][2] DBA in block mismatch [513][1159680]
DUL: Warning: File=1, block 2: illegal block version 2
DUL: Warning: Block[1][2] Illegal block type[0]
DUL: Warning: Bad cache layer header file#=1, block#=2

DUL: Warning: Block[1][4] DBA in block mismatch [1][2]
DUL: Warning: File[1]Block[4]INCSEQ mismatch[90268!=0]
DUL: Warning: Bad cache layer header file#=1, block#=4

DUL: Warning: Block[1][6] DBA in block mismatch [1][3]
DUL: Warning: File[1]Block[6]INCSEQ mismatch[139591710!=86360346]
DUL: Warning: Bad cache layer header file#=1, block#=6

...........and etc..........

QUOTE MISSING

If you get the follwing error it is caused by the data dictionary tables "USER$, OBJ$, TAB$ and COL$" not being correctly generated. To fix this error simply delete all dictv6.ddl or dictv7.ddl created .dat and .ctl files and restart.

Data UnLoader: Release 3.2.0.1 - Internal Use Only - on Wed Sep 3 10:49:30 1997
Copyright (c) 1994/95 Oracle Corporation, The Netherlands. All rights reserved.
DUL: Error: Quote missing

SQL*Loader problems and work arounds

233827 LOADER REJECTS MULTI-LINE RECORDS IF USING 'TERMINATED BY WHITESPACE'
DESCRIPTION: Load of multi line records fails if the continuation is between columns.
WORK AROUND: Use larger physical records (init.dul: LDR_PHYS_REC_SIZE)
FIXED: 7.3
250325 CANNOT LOAD CHAR THAT'S USED AS ENCLOSING CHARACTER
DESCRIPTION: The stutter syntax of a column that starts with an enclosing character is not parsed correctly. ("""string itself enclosed in quotes""" is not parsed correctly).
WORK AROUND: Use other enclosing character. (init.dul: LDR_ENCLOSE_CHAR)
FIXED: 7.1.6

Script to unload USER$, OBJ$, TAB$ and COL$

REM DDL Script to unload the dictionary cache for DUL V3 (Oracle 7)
REM force the settings, so I know what happens
alter session set export_mode = false;
alter session set ldr_phys_rec_size = 0;
alter session set ldr_enclose_char = """" ;
alter session set file = "" ;
alter session set max_unload_blocks = 0;
alter session set blocks_to_skip = 0;

unload table OBJ$ ( OBJ# number, OWNER# number, NAME varchar2(30),
        NAMESPACE ignore, TYPE number)
        storage( objno 17 file 1);

unload table TAB$( OBJ# number, TS# ignore, FILE# number, BLOCK# number,
        CLU# ignore, TAB# number, COLS number, CLUCOLS number)
        cluster  C_OBJ#(OBJ#)
        storage ( tabno 1 segobjno 1 file 1)
;

unload table COL$ ( OBJ# number, COL# number , SEGCOL# number,
        SEGCOLLENGTH ignore, OFFSET ignore, NAME char(30),
        TYPE# number, LENGTH number)
        cluster C_OBJ#(OBJ#)
        storage( tabno 5 segobjno 1 file 1)
;

unload table USER$( USER# number, NAME varchar2(30))
        cluster C_USER#(USER#)
        storage(tabno 1 segobjno 9 file 1)
;

REM restart and load the dictinary in the cache
exit

Bernard van Duijnen