Export and Import

These tools are used to transfer data from one oracle database to another oracle database. You Export tool to export data from source database, and Import tool to load data into the target database. When you export tables from source database export tool will extracts the tables and puts it into the dump file. This dump file is transferred to the target database. At the target database the Import tool will copy the data from dump file to the target database.

From Ver. 10g Oracle is recommending to use Data Pump Export and Import tools, which are enhanced versions of original Export and Import tools.

The export dump file contains objects in the following order:

1. Type definitions
2. Table definitions
3. Table data
4. Table indexes
5. Integrity constraints, views, procedures, and triggers
6. Bitmap, function-based, and domain indexes

When you import the tables the import tool will perform the actions in the following order, new tables are created, data is imported and indexes are built, triggers are imported, integrity constraints are enabled on the new tables, and any bitmap, function-based, and/or domain indexes are built. This sequence prevents data from being rejected due to the order in which tables are imported. This sequence also prevents redundant triggers from firing twice on the same data

Invoking Export and Import

You can run Export and Import tool in two modes

            Command Line Mode

            Interactive Mode

When you just type exp or imp at o/s prompt it will run in interactive mode i.e. these tools will prompt you for all the necessary input. If you supply command line arguments when calling exp or imp then it will run in command line mode

Command Line Parameters of Export tool

You can control how Export runs by entering the EXP command followed
by various arguments. To specify parameters, you use keywords:

     Format:  EXP KEYWORD=value or KEYWORD=(value1,value2,...,valueN)

     Example: EXP SCOTT/TIGER GRANTS=Y TABLES=(EMP,DEPT,MGR)

               or TABLES=(T1:P1,T1:P2), if T1 is partitioned table

Keyword                               Description (Default)                    

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

USERID                                 username/password                     

BUFFER                                                size of data buffer                         

FILE                                         output files (EXPDAT.DMP)       

COMPRESS                          import into one extent (Y)         

GRANTS                               export grants (Y)                             

INDEXES                               export indexes (Y)                          

DIRECT                                  direct path (N)                                 

LOG                                       log file of screen output               

ROWS                                   export data rows (Y)                      

CONSISTENT                     cross-table consistency(N)         

 FULL                                    export entire file (N)

 OWNER                               list of owner usernames

TABLES                                 list of table names

 RECORDLENGTH              length of IO record

 INCTYPE                              incremental export type

 RECORD                              track incr. export (Y)

TRIGGERS                            export triggers (Y)

 STATISTICS                         analyze objects (ESTIMATE)

 PARFILE                               parameter filename

CONSTRAINTS                   export constraints (Y)
OBJECT_CONSISTENT    transaction set to read only during object export (N)

FEEDBACK                           display progress every x rows (0)

FILESIZE                                maximum size of each dump file

FLASHBACK_SCN             SCN used to set session snapshot back to

FLASHBACK_TIME           time used to get the SCN closest to the specified time

QUERY                                  select clause used to export a subset of a table

RESUMABLE                       suspend when a space related error is encountered(N)

RESUMABLE_NAME       text string used to identify resumable statement

RESUMABLE_TIMEOUT    wait time for RESUMABLE

TTS_FULL_CHECK             perform full or partial dependency check for TTS

TABLESPACES                    list of tablespaces to export

TRANSPORT_TABLESPACE           export transportable tablespace metadata (N)

TEMPLATE                           template name which invokes iAS mode export

The Export and Import tools support four modes of operation

                        FULL               :Exports all the objects in all schemas
                        OWNER             :Exports objects only belonging to the given OWNER
                        TABLES           :Exports Individual Tables
                        TABLESPACE  :Export all objects located in a given TABLESPACE.

Example of Exporting Full Database

The following example shows how to export full database

$exp USERID=scott/tiger FULL=y FILE=myfull.dmp

In the above command, FILE option specifies the name of the dump file, FULL option specifies that you want to export the full database, USERID option specifies the user account to connect to the database. Note, to perform full export the user should have DBA or EXP_FULL_DATABASE privilege. 

 Example of Exporting Schemas

To export Objects stored in a particular schemas you can run export utility with the following arguments

$exp USERID=scott/tiger OWNER=(SCOTT,ALI) FILE=exp_own.dmp

The above command will export all the objects stored in SCOTT and ALI’s schema.

Exporting Individual Tables

To export individual tables give the following command

$exp USERID=scott/tiger TABLES=(scott.emp,scott.sales) FILE=exp_tab.dmp

This will export scott’s emp and sales tables.

Exporting Consistent Image of the tables

If you include CONSISTENT=Y option in export command argument then, Export utility will export a consistent image of the table i.e. the changes which are done to the table during export operation will not be exported.

Using Import Utility

Objects exported by export utility can only be imported by Import utility. Import utility can  run in Interactive mode or command line mode.

You can let Import prompt you for parameters by entering the IMP command followed by your username/password:

     Example: IMP SCOTT/TIGER

Or, you can control how Import runs by entering the IMP command followed

by various arguments. To specify parameters, you use keywords:

     Format:  IMP KEYWORD=value or KEYWORD=(value1,value2,...,valueN)

     Example: IMP SCOTT/TIGER IGNORE=Y TABLES=(EMP,DEPT) FULL=N

               or TABLES=(T1:P1,T1:P2), if T1 is partitioned table

USERID must be the first parameter on the command line.

Example Importing Individual Tables

To import individual tables from a full database export dump file give the following command

$imp scott/tiger FILE=myfullexp.dmp FROMUSER=scott TABLES=(emp,dept)

This command will import only emp, dept tables into Scott user and you will get a output similar  to as shown below

Export file created by EXPORT:V10.00.00 via conventional path

import done in WE8DEC character set and AL16UTF16 NCHAR character set

. importing SCOTT's objects into SCOTT

. . importing table                         "DEPT"          4 rows imported

. . importing table                          "EMP"         14 rows imported

Import terminated successfully without warnings.

Example, Importing Tables of One User account into another User account

For example, suppose Ali has exported tables into a dump file mytables.dmp. Now Scott wants to import these tables. To achieve this Scott will give the following import command

$imp scott/tiger  FILE=mytables.dmp FROMUSER=ali TOUSER=scott

Then import utility will give a warning that tables in the dump file was exported by user Ali and not you and then proceed.

Example Importing Tables Using Pattern Matching

Suppose you want to import all tables from a dump file whose name matches a particular pattern. To do so, use “%” wild character in TABLES option. For example, the following command will import all tables whose names starts with alphabet “e” and those tables whose name contains alphabet “d”

$imp scott/tiger FILE=myfullexp.dmp FROMUSER=scott TABLES=(a%,%d%)

Migrating a Database across platforms.

The Export and Import utilities are the only method that Oracle supports for moving an existing Oracle database from one hardware platform to another. This includes moving between UNIX and NT systems and also moving between two NT systems running on different platforms.

The following steps present a general overview of how to move a database between platforms.

1. As a DBA user, issue the following SQL query to get the exact name of all tablespaces. You will need this information later in the process.

SQL> SELECT tablespace_name FROM dba_tablespaces;

2. As a DBA user, perform a full export from the source database, for example:

> exp system/manager FULL=y FILE=myfullexp.dmp

3. Move the dump file to the target database server. If you use FTP, be sure to copy it in binary format (by entering binary at the FTP prompt) to avoid file corruption.
4. Create a database on the target server.
5. Before importing the dump file, you must first create your tablespaces, using the information obtained in Step 1. Otherwise, the import will create the corresponding datafiles in the same file structure as at the source database, which may not be compatible with the file structure on the target system.
6. As a DBA user, perform a full import with the IGNORE parameter enabled:

> imp system/manager FULL=y IGNORE=y FILE=myfullexp.dmp

Using IGNORE=y instructs Oracle to ignore any creation errors during the import and permit the import to complete.

7. Perform a full backup of your new database.