Unlock Oracle Data Recovery with Free gDUL 3.0: Features, Setup & Best Practices

Overview

gDUL 3.0 is a free Oracle database recovery utility that can read table data directly when the database cannot be opened. It supports export to EXPDP, EXP, and text formats.

Key Features

Exports in EXPDP, EXP, and text formats; only gDUL among similar tools supports EXPDP.

Built‑in asmcmd support for ASM file systems.

Handles most column types (NUMBER, CHAR, VARCHAR2, DATE, LOB, LONG, etc.).

Single executable per platform (HP‑UX, AIX, Solaris, Linux, Windows).

Free for use (not open‑source).

Directory Structure

root : setup (ASM and data‑file list configuration) and gdul (executable).

conf : gdul.ini (parameter file), datafile.ini (data‑file list), asmdisk.ini (ASM disk list).

dict : *.dat (SYS user dictionary data).

dump : *.dmp, *.dat (exported dump/text files).

log : gdul.log (main log) and unload_table.log (table export log).

sample : *.dict, *.dat (sample row data when no SYSTEM tablespace exists).

bin_file : platform‑specific gdul executables.

gdul.ini Parameters

db_compat_version : Database version (9, 10, 11, 12). Default = 10.

db_block_size : Default block size (4096, 8192, 16384, 32768). Default = 8192.

file_raw_offset : File header offset for AIX (0 or 4096). Default = 0.

reverse_byte : Read data from different CPU platforms (false/true). Default = false.

export_format : Export format (SQLLDR, EXP, EXPDP). Default = EXPDP.

ldr_enclose_char : Field delimiter for text export (ASCII character). Default = |.

trace_block : Trace block during export (false/true). Default = false.

Best‑Practice Workflow

Configure gdul.ini, asmdisk.ini, and datafile.ini. Use the setup script when the database is mounted or opened.

Set export_format to EXPDP (edit conf/gdul.ini).

Initialize the data dictionary.

Display the list of database users.

Export a single table.

Export all tables belonging to a specific user.

Recover truncated tables by scanning the tablespace and unloading rows.

GDUL> bootstrap
Bootstrap finish.

Platform‑Specific Notes

AIX Bare LV

If a raw LV has a 4 KB header, set offset=4096 in datafile.ini. For ASM disks, check DEVICESUBTYPE with lslv -L <LV_NAME> and adjust asmdisk.ini accordingly.

Linux Bare Devices

Linux raw devices cannot be accessed as regular files. Replace /dev/rawN with the associated block device (found via cat /etc/sysconfig/rawdevices) in datafile.ini or asmdisk.ini.

Windows

Windows does not run the setup script. Manually create the directories conf, dict, log, dump, sample and place gdul.ini, datafile.ini, and asmdisk.ini inside conf. Ensure db_compat_version matches the target Oracle version.

Download

The gDUL 3.0 binary is freely available from the DBA+ community repository.