21 Original Export

Running catexp.sql or catalog.sql

To use Export, you must run the script catexp.sql or catalog.sql (which runs catexp.sql) after the database has been created or migrated to a newer release.

The catexp.sql or catalog.sql script needs to be run only once on a database. The script performs the following tasks to prepare the database for export and import operations:

• Creates the necessary export and import views in the data dictionary

• Creates the EXP_FULL_DATABASE and IMP_FULL_DATABASE roles

• Assigns all necessary privileges to the EXP_FULL_DATABASE and IMP_FULL_DATABASE roles

• Assigns EXP_FULL_DATABASE and IMP_FULL_DATABASE to the DBA role

• Records the version of catexp.sql that has been installed

The EXP_FULL_DATABASE and IMP_FULL_DATABASE roles are powerful. Database administrators should use caution when granting these roles to users.

Ensuring Sufficient Disk Space for Export Operations

Before you run Export, ensure that there is sufficient disk or tape storage space to write the export file. If there is not enough space, then Export terminates with a write-failure error.

You can use table sizes to estimate the maximum space needed. You can find table sizes in the USER_SEGMENTS view of the Oracle data dictionary. The following query displays disk usage for all tables:

SELECT SUM(BYTES) FROM USER_SEGMENTS WHERE SEGMENT_TYPE='TABLE';

The result of the query does not include disk space used for data stored in LOB (large object) or VARRAY columns or in partitioned tables.

Verifying Access Privileges for Export and Import Operations

To use Export, you must have the CREATE SESSION privilege on an Oracle database. This privilege belongs to the CONNECT role established during database creation. To export tables owned by another user, you must have the EXP_FULL_DATABASE role enabled. This role is granted to all database administrators (DBAs).

If you do not have the system privileges contained in the EXP_FULL_DATABASE role, then you cannot export objects contained in another user's schema. For example, you cannot export a table in another user's schema, even if you created a synonym for it.

Several system schemas cannot be exported because they are not user schemas; they contain Oracle-managed data and metadata. Examples of schemas that are not exported include SYS, ORDSYS, and MDSYS.

Invoking Export as SYSDBA

SYSDBA is used internally and has specialized functions; its behavior is not the same as for generalized users. Therefore, you should not typically need to invoke Export as SYSDBA except in the following situations:

• At the request of Oracle technical support

• When importing a transportable tablespace set

Command-Line Entries

You can specify all valid parameters and their values from the command line using the following syntax (you will then be prompted for a username and password):

exp PARAMETER=value

or

exp PARAMETER=(value1,value2,...,valuen)

The number of parameters cannot exceed the maximum length of a command line on the system.

Parameter Files

You can specify all valid parameters and their values in a parameter file. Storing the parameters in a file allows them to be easily modified or reused, and is the recommended method for invoking Export. If you use different parameters for different databases, then you can have multiple parameter files.

Create the parameter file using any flat file text editor. The command-line option PARFILE=filename tells Export to read the parameters from the specified file rather than from the command line. For example:

The syntax for parameter file specifications is one of the following:

PARAMETER=value
PARAMETER=(value)
PARAMETER=(value1, value2, ...)

The following example shows a partial parameter file listing:

FULL=y
FILE=dba.dmp
GRANTS=y
INDEXES=y
CONSISTENT=y

You can add comments to the parameter file by preceding them with the pound (#) sign. Export ignores all characters to the right of the pound (#) sign.

You can specify a parameter file at the same time that you are entering parameters on the command line. In fact, you can specify the same parameter in both places. The position of the PARFILE parameter and other parameters on the command line determines which parameters take precedence. For example, assume the parameter file params.dat contains the parameter INDEXES=y and Export is invoked with the following line:

exp PARFILE=params.dat INDEXES=n

In this case, because INDEXES=n occurs after PARFILE=params.dat, INDEXES=n overrides the value of the INDEXES parameter in the parameter file.

Interactive Mode

If you prefer to be prompted for the value of each parameter, then you can simply specify either exp at the command line. You will be prompted for a username and password.

Commonly used parameters are then displayed. You can accept the default value, if one is provided, or enter a different value. The command-line interactive method does not provide prompts for all functionality and is provided only for backward compatibility. If you want to use an interactive interface, then Oracle recommends that you use the Oracle Enterprise Manager Export Wizard.

Getting Online Help

Export provides online help. Enter exp help=y on the command line to invoke Export help.

Table-Level and Partition-Level Export

You can export tables, partitions, and subpartitions in the following ways:

• Table-level Export: exports all data from the specified tables

• Partition-level Export: exports only data from the specified source partitions or subpartitions

In all modes, partitioned data is exported in a format such that partitions or subpartitions can be imported selectively.

BUFFER

Default: operating system-dependent. See your Oracle operating system-specific documentation to determine the default value for this parameter.

Specifies the size, in bytes, of the buffer used to fetch rows. As a result, this parameter determines the maximum number of rows in an array fetched by Export. Use the following formula to calculate the buffer size:

buffer_size = rows_in_array * maximum_row_size

If you specify zero, then the Export utility fetches only one row at a time.

Tables with columns of type LOBs, LONG, BFILE, REF, ROWID, LOGICAL ROWID, or DATE are fetched one row at a time.

CREATE TABLE sample (name varchar(30), weight number);

COMPRESS

Default: y

Specifies how Export and Import manage the initial extent for table data.

The default, COMPRESS=y, causes Export to flag table data for consolidation into one initial extent upon import. If extent sizes are large (for example, because of the PCTINCREASE parameter), then the allocated space will be larger than the space required to hold the data.

If you specify COMPRESS=n, then Export uses the current storage parameters, including the values of initial extent size and next extent size. The values of the parameters may be the values specified in the CREATE TABLE or ALTER TABLE statements or the values modified by the database system. For example, the NEXT extent size value may be modified if the table grows and if the PCTINCREASE parameter is nonzero.

The COMPRESS parameter does not work with bitmapped tablespaces.

CONSISTENT

Default: n

Specifies whether Export uses the SET TRANSACTION READ ONLY statement to ensure that the data seen by Export is consistent to a single point in time and does not change during the execution of the exp command. You should specify CONSISTENT=y when you anticipate that other applications will be updating the target data after an export has started.

If you use CONSISTENT=n, then each table is usually exported in a single transaction. However, if a table contains nested tables, then the outer table and each inner table are exported as separate transactions. If a table is partitioned, then each partition is exported as a separate transaction.

Therefore, if nested tables and partitioned tables are being updated by other applications, then the data that is exported could be inconsistent. To minimize this possibility, export those tables at a time when updates are not being done.

Table 21-2 shows a sequence of events by two users: user1 exports partitions in a table and user2 updates data in that table.

If the export uses CONSISTENT=y, then none of the updates by user2 are written to the export file.

If the export uses CONSISTENT=n, then the updates to TAB:P1 are not written to the export file. However, the updates to TAB:P2 are written to the export file, because the update transaction is committed before the export of TAB:P2 begins. As a result, the user2 transaction is only partially recorded in the export file, making it inconsistent.

If you use CONSISTENT=y and the volume of updates is large, then the rollback segment usage will be large. In addition, the export of each table will be slower, because the rollback segment must be scanned for uncommitted transactions.

Keep in mind the following points about using CONSISTENT=y:

• CONSISTENT=y is unsupported for exports that are performed when you are connected as user SYS or you are using AS SYSDBA, or both.

• Export of certain metadata may require the use of the SYS schema within recursive SQL. In such situations, the use of CONSISTENT=y will be ignored. Oracle recommends that you avoid making metadata changes during an export process in which CONSISTENT=y is selected.

• To minimize the time and space required for such exports, you should export tables that need to remain consistent separately from those that do not. For example, export the emp and dept tables together in a consistent export, and then export the remainder of the database in a second pass.

• A "snapshot too old" error occurs when rollback space is used up, and space taken up by committed transactions is reused for new transactions. Reusing space in the rollback segment allows database integrity to be preserved with minimum space requirements, but it imposes a limit on the amount of time that a read-consistent image can be preserved.

  If a committed transaction has been overwritten and the information is needed for a read-consistent view of the database, then a "snapshot too old" error results.

  To avoid this error, you should minimize the time taken by a read-consistent export. (Do this by restricting the number of objects exported and, if possible, by reducing the database transaction rate.) Also, make the rollback segment as large as possible.

  Note:

  Rollback segments will be deprecated in a future Oracle database release. Oracle recommends that you use automatic undo management instead.

  See Also:

  "OBJECT_CONSISTENT"

CONSTRAINTS

Default: y

Specifies whether the Export utility exports table constraints.

DIRECT

Default: n

Specifies the use of direct path Export.

Specifying DIRECT=y causes Export to extract data by reading the data directly, bypassing the SQL command-processing layer (evaluating buffer). This method can be much faster than a conventional path Export.

For information about direct path Exports, including security and performance considerations, see "Invoking a Direct Path Export".

FEEDBACK

Default: 0 (zero)

Specifies that Export should display a progress meter in the form of a period for n number of rows exported. For example, if you specify FEEDBACK=10, then Export displays a period each time 10 rows are exported. The FEEDBACK value applies to all tables being exported; it cannot be set individually for each table.

FILE

Default: expdat.dmp

Specifies the names of the export dump files. The default extension is .dmp, but you can specify any extension. Because Export supports multiple export files, you can specify multiple file names to be used. For example:

exp scott FILE = dat1.dmp, dat2.dmp, dat3.dmp FILESIZE=2048

When Export reaches the value you have specified for the maximum FILESIZE, Export stops writing to the current file, opens another export file with the next name specified by the FILE parameter, and continues until complete or the maximum value of FILESIZE is again reached. If you do not specify sufficient export file names to complete the export, then Export prompts you to provide additional file names.

FILESIZE

Default: Data is written to one file until the maximum size, as specified in Table 21-3, is reached.

Export supports writing to multiple export files, and Import can read from multiple export files. If you specify a value (byte limit) for the FILESIZE parameter, then Export will write only the number of bytes you specify to each dump file.

When the amount of data Export must write exceeds the maximum value you specified for FILESIZE, it will get the name of the next export file from the FILE parameter (see "FILE" for more information) or, if it has used all the names specified in the FILE parameter, then it will prompt you to provide a new export file name. If you do not specify a value for FILESIZE (note that a value of 0 is equivalent to not specifying FILESIZE), then Export will write to only one file, regardless of the number of files specified in the FILE parameter.

The FILESIZE parameter has a maximum value equal to the maximum value that can be stored in 64 bits.

Table 21-3 shows that the maximum size for dump files depends on the operating system you are using and on the release of the Oracle database that you are using.

The maximum value that can be stored in a file is dependent on your operating system. You should verify this maximum value in your Oracle operating system-specific documentation before specifying FILESIZE. You should also ensure that the file size you specify for Export is supported on the system on which Import will run.

The FILESIZE value can also be specified as a number followed by KB (number of kilobytes). For example, FILESIZE=2KB is the same as FILESIZE=2048. Similarly, MB specifies megabytes (1024 * 1024) and GB specifies gigabytes (1024**3). B remains the shorthand for bytes; the number is not multiplied to obtain the final file size (FILESIZE=2048B is the same as FILESIZE=2048).

FLASHBACK_SCN

Default: none

Specifies the system change number (SCN) that Export will use to enable flashback. The export operation is performed with data consistent as of this specified SCN.

The following is an example of specifying an SCN. When the export is performed, the data will be consistent as of SCN 3482971.

> exp FILE=exp.dmp FLASHBACK_SCN=3482971

FLASHBACK_TIME

Default: none

Enables you to specify a timestamp. Export finds the SCN that most closely matches the specified timestamp. This SCN is used to enable flashback. The export operation is performed with data consistent as of this SCN.

You can specify the time in any format that the DBMS_FLASHBACK.ENABLE_AT_TIME procedure accepts. This means that you can specify it in either of the following ways:

> exp FILE=exp.dmp FLASHBACK_TIME="TIMESTAMP '2006-05-01 11:00:00'"

> exp FILE=exp.dmp FLASHBACK_TIME="TO_TIMESTAMP('12-02-2005 14:35:00', 'DD-MM-YYYY HH24:MI:SS')"

Also, the old format, as shown in the following example, will continue to be accepted to ensure backward compatibility:

> exp FILE=exp.dmp FLASHBACK_TIME="'2006-05-01 11:00:00'"

FULL

Default: n

Indicates that the export is a full database mode export (that is, it exports the entire database). Specify FULL=y to export in full database mode. You need to have the EXP_FULL_DATABASE role to export in this mode.

GRANTS

Default: y

Specifies whether the Export utility exports object grants. The object grants that are exported depend on whether you use full database mode or user mode. In full database mode, all grants on a table are exported. In user mode, only those granted by the owner of the table are exported. System privilege grants are always exported.

HELP

Default: none

Displays a description of the Export parameters. Enter exp help=y on the command line to invoke it.

INDEXES

Default: y

Specifies whether the Export utility exports indexes.

LOG

Default: none

Specifies a file name (for example, export.log) to receive informational and error messages.

If you specify this parameter, then messages are logged in the log file and displayed to the terminal display.

OBJECT_CONSISTENT

Default: n

Specifies whether the Export utility uses the SET TRANSACTION READ ONLY statement to ensure that the data exported is consistent to a single point in time and does not change during the export. If OBJECT_CONSISTENT is set to y, then each object is exported in its own read-only transaction, even if it is partitioned. In contrast, if you use the CONSISTENT parameter, then there is only one read-only transaction.

OWNER

Default: none

Indicates that the export is a user-mode export and lists the users whose objects will be exported. If the user initiating the export is the database administrator (DBA), then multiple users can be listed.

User-mode exports can be used to back up one or more database users. For example, a DBA may want to back up the tables of deleted users for a period of time. User mode is also appropriate for users who want to back up their own data or who want to move objects from one owner to another.

PARFILE

Default: none

Specifies a file name for a file that contains a list of Export parameters. For more information about using a parameter file, see "Invoking Export".

QUERY

Default: none

This parameter enables you to select a subset of rows from a set of tables when doing a table mode export. The value of the query parameter is a string that contains a WHERE clause for a SQL SELECT statement that will be applied to all tables (or table partitions) listed in the TABLES parameter.

For example, if user scott wants to export only those employees whose job title is SALESMAN and whose salary is less than 1600, then he could do the following (this example is UNIX-based):

exp scott TABLES=emp QUERY=\"WHERE job=\'SALESMAN\' and sal \<1600\"

When executing this query, Export builds a SQL SELECT statement similar to the following:

SELECT * FROM emp WHERE job='SALESMAN' and sal <1600; 
 

The values specified for the QUERY parameter are applied to all tables (or table partitions) listed in the TABLES parameter. For example, the following statement will unload rows in both emp and bonus that match the query:

exp scott TABLES=emp,bonus QUERY=\"WHERE job=\'SALESMAN\' and sal\<1600\"
 

Again, the SQL statements that Export executes are similar to the following:

SELECT * FROM emp WHERE job='SALESMAN' and sal <1600;

SELECT * FROM bonus WHERE job='SALESMAN' and sal <1600;

If a table is missing the columns specified in the QUERY clause, then an error message will be produced, and no rows will be exported for the offending table.

RECORDLENGTH

Default: operating system-dependent

Specifies the length, in bytes, of the file record. The RECORDLENGTH parameter is necessary when you must transfer the export file to another operating system that uses a different default value.

If you do not define this parameter, then it defaults to your platform-dependent value for buffer size.

You can set RECORDLENGTH to any value equal to or greater than your system's buffer size. (The highest value is 64 KB.) Changing the RECORDLENGTH parameter affects only the size of data that accumulates before writing to the disk. It does not affect the operating system file block size.

RESUMABLE

Default: n

The RESUMABLE parameter is used to enable and disable resumable space allocation. Because this parameter is disabled by default, you must set RESUMABLE=y to use its associated parameters, RESUMABLE_NAME and RESUMABLE_TIMEOUT.

RESUMABLE_NAME

Default: 'User USERNAME (USERID), Session SESSIONID, Instance INSTANCEID'

The value for this parameter identifies the statement that is resumable. This value is a user-defined text string that is inserted in either the USER_RESUMABLE or DBA_RESUMABLE view to help you identify a specific resumable statement that has been suspended.

This parameter is ignored unless the RESUMABLE parameter is set to y to enable resumable space allocation.

RESUMABLE_TIMEOUT

Default: 7200 seconds (2 hours)

The value of the parameter specifies the time period during which an error must be fixed. If the error is not fixed within the timeout period, then execution of the statement is terminated.

This parameter is ignored unless the RESUMABLE parameter is set to y to enable resumable space allocation.

ROWS

Default: y

Specifies whether the rows of table data are exported.

STATISTICS

Default: ESTIMATE

Specifies the type of database optimizer statistics to generate when the exported data is imported. Options are ESTIMATE, COMPUTE, and NONE.

In some cases, Export will place the precalculated statistics in the export file, and also the ANALYZE statements to regenerate the statistics.

However, the precalculated optimizer statistics will not be used at export time if a table has columns with system-generated names.

The precalculated optimizer statistics are flagged as questionable at export time if:

• There are row errors while exporting

• The client character set or NCHAR character set does not match the server character set or NCHAR character set

• A QUERY clause is specified

• Only certain partitions or subpartitions are exported

  Note:

  Specifying ROWS=n does not preclude saving the precalculated statistics in the export file. This enables you to tune plan generation for queries in a nonproduction database using statistics from a production database.

TABLES

Default: none

Specifies that the export is a table-mode export and lists the table names and partition and subpartition names to export. You can specify the following when you specify the name of the table:

• schemaname specifies the name of the user's schema from which to export the table or partition. If a schema name is not specified, then the exporter's schema is used as the default. System schema names such as ORDSYS, MDSYS, CTXSYS, LBACSYS, and ORDPLUGINS are reserved by Export.

• tablename specifies the name of the table or tables to be exported. Table-level export lets you export entire partitioned or nonpartitioned tables. If a table in the list is partitioned and you do not specify a partition name, then all its partitions and subpartitions are exported.

  The table name can contain any number of '%' pattern matching characters, which can each match zero or more characters in the table name against the table objects in the database. All the tables in the relevant schema that match the specified pattern are selected for export, as if the respective table names were explicitly specified in the parameter.

• partition_name indicates that the export is a partition-level Export. Partition-level Export lets you export one or more specified partitions or subpartitions within a table.

The syntax you use to specify the preceding is in the form:

schemaname.tablename:partition_name
schemaname.tablename:subpartition_name

If you use tablename:partition_name, then the specified table must be partitioned, and partition_name must be the name of one of its partitions or subpartitions. If the specified table is not partitioned, then the partition_name is ignored and the entire table is exported.

See "Example Export Session Using Partition-Level Export" for several examples of partition-level Exports.

TABLESPACES

Default: none

The TABLESPACES parameter specifies that all tables in the specified tablespace be exported to the Export dump file. This includes all tables contained in the list of tablespaces and all tables that have a partition located in the list of tablespaces. Indexes are exported with their tables, regardless of where the index is stored.

You must have the EXP_FULL_DATABASE role to use TABLESPACES to export all tables in the tablespace.

When TABLESPACES is used in conjunction with TRANSPORT_TABLESPACE=y, you can specify a limited list of tablespaces to be exported from the database to the export file.

TRANSPORT_TABLESPACE

Default: n

When specified as y, this parameter enables the export of transportable tablespace metadata.

Encrypted columns are not supported in transportable tablespace mode.

TRIGGERS

Default: y

Specifies whether the Export utility exports triggers.

TTS_FULL_CHECK

Default: n

When TTS_FULL_CHECK is set to y, Export verifies that a recovery set (set of tablespaces to be recovered) has no dependencies (specifically, IN pointers) on objects outside the recovery set, and the reverse.

USERID (username/password)

Default: none

Specifies the username, password, and optional connect string of the user performing the export. If you omit the password, then Export will prompt you for it.

If you connect as user SYS, then you must also specify AS SYSDBA in the connect string. Your operating system may require you to treat AS SYSDBA as a special string, in which case the entire string would be enclosed in quotation marks.

VOLSIZE

Default: none

Specifies the maximum number of bytes in an export file on each volume of tape.

The VOLSIZE parameter has a maximum value equal to the maximum value that can be stored in 64 bits on your platform.

The VOLSIZE value can be specified as a number followed by KB (number of kilobytes). For example, VOLSIZE=2KB is the same as VOLSIZE=2048. Similarly, MB specifies megabytes (1024 * 1024) and GB specifies gigabytes (1024**3). B remains the shorthand for bytes; the number is not multiplied to get the final file size (VOLSIZE=2048B is the same as VOLSIZE=2048).

Example Export Session in Full Database Mode

Only users with the DBA role or the EXP_FULL_DATABASE role can export in full database mode. In this example, an entire database is exported to the file dba.dmp with all GRANTS and all data.

Parameter File Method

> exp PARFILE=params.dat

The params.dat file contains the following information:

FILE=dba.dmp
GRANTS=y
FULL=y
ROWS=y

Command-Line Method

> exp FULL=y FILE=dba.dmp GRANTS=y ROWS=y

Export Messages

Information is displayed about the release of Export you are using and the release of Oracle Database that you are connected to. Status messages are written out as the entire database is exported. A final completion message is returned when the export completes successfully, without warnings.

Example Export Session in User Mode

User-mode exports can be used to back up one or more database users. For example, a DBA may want to back up the tables of deleted users for a period of time. User mode is also appropriate for users who want to back up their own data or who want to move objects from one owner to another. In this example, user scott is exporting his own tables.

Parameter File Method

> exp scott PARFILE=params.dat

The params.dat file contains the following information:

FILE=scott.dmp
OWNER=scott
GRANTS=y
ROWS=y
COMPRESS=y

Command-Line Method

> exp scott FILE=scott.dmp OWNER=scott GRANTS=y ROWS=y COMPRESS=y 

Export Messages

Information is displayed about the release of Export you are using and the release of Oracle Database that you are connected to. Then, status messages similar to the following are shown:

.
.
. about to export SCOTT's tables via Conventional Path ...
. . exporting table                          BONUS          0 rows exported
. . exporting table                           DEPT          4 rows exported
. . exporting table                            EMP         14 rows exported
. . exporting table                       SALGRADE          5 rows exported
.
.
.
Export terminated successfully without warnings.

Example Export Sessions in Table Mode

In table mode, you can export table data or the table definitions. (If no rows are exported, then the CREATE TABLE statement is placed in the export file, with grants and indexes, if they are specified.)

A user with the EXP_FULL_DATABASE role can use table mode to export tables from any user's schema by specifying TABLES=schemaname.tablename.

If schemaname is not specified, then Export defaults to the exporter's schema name. In the following example, Export defaults to the SYSTEM schema for table a and table c:

> exp TABLES=(a, scott.b, c, mary.d)

A user with the EXP_FULL_DATABASE role can also export dependent objects that are owned by other users. A nonprivileged user can export only dependent objects for the specified tables that the user owns.

Exports in table mode do not include cluster definitions. As a result, the data is exported as unclustered tables. Thus, you can use table mode to uncluster tables.

> exp PARFILE=params.dat

FILE=expdat.dmp
TABLES=(scott.emp,blake.dept)
GRANTS=y
INDEXES=y

> exp FILE=expdat.dmp TABLES=(scott.emp,blake.dept) GRANTS=y INDEXES=y

.
.
.
About to export specified tables via Conventional Path ...
Current user changed to SCOTT
. . exporting table                            EMP         14 rows exported
Current user changed to BLAKE
. . exporting table                           DEPT          8 rows exported
Export terminated successfully without warnings.

> exp blake PARFILE=params.dat

FILE=blake.dmp
TABLES=(dept,manager)
ROWS=y
COMPRESS=y

> exp blake FILE=blake.dmp TABLES=(dept, manager) ROWS=y COMPRESS=y

.
.
.

About to export specified tables via Conventional Path ...
. . exporting table                           DEPT          8 rows exported
. . exporting table                        MANAGER          4 rows exported
Export terminated successfully without warnings.

> exp PARFILE=params.dat

FILE=misc.dmp
TABLES=(scott.%P%,blake.%,scott.%S%)

> exp FILE=misc.dmp TABLES=(scott.%P%,blake.%,scott.%S%)

.
.
.
About to export specified tables via Conventional Path ...
Current user changed to SCOTT
. . exporting table                           DEPT          4 rows exported
. . exporting table                            EMP         14 rows exported
Current user changed to BLAKE
. . exporting table                           DEPT          8 rows exported
. . exporting table                        MANAGER          4 rows exported
Current user changed to SCOTT
. . exporting table                          BONUS          0 rows exported
. . exporting table                       SALGRADE          5 rows exported
Export terminated successfully without warnings.

Example Export Session Using Partition-Level Export

In partition-level Export, you can specify the partitions and subpartitions of a table that you want to export.

> exp scott PARFILE=params.dat

TABLES=(emp)
ROWS=y

> exp scott TABLES=emp rows=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting partition                              M          8 rows exported
. . exporting partition                              Z          6 rows exported
Export terminated successfully without warnings.

 > exp scott PARFILE=params.dat

TABLES=(emp:m)
ROWS=y

> exp scott TABLES=emp:m rows=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting partition                              M          8 rows exported
Export terminated successfully without warnings.

> exp scott PARFILE=params.dat

TABLES=(emp:m,emp:sp4)
ROWS=y

> exp scott TABLES=(emp:m, emp:sp4) ROWS=y

.
.
.
About to export specified tables via Conventional Path ...
. . exporting table                            EMP
. . exporting composite partition                    M
. . exporting subpartition                         SP1          1 rows exported
. . exporting subpartition                         SP2          3 rows exported
. . exporting composite partition                    Z
. . exporting subpartition                         SP4          1 rows exported
Export terminated successfully without warnings.

Log File

You can capture all Export messages in a log file, either by using the LOG parameter or, for those systems that permit it, by redirecting the output to a file. A log of detailed information is written about successful unloads and any errors that may have occurred.

Warning Messages

Export does not terminate after recoverable errors. For example, if an error occurs while exporting a table, then Export displays (or logs) an error message, skips to the next table, and continues processing. These recoverable errors are known as warnings.

Export also issues warnings when invalid objects are encountered.

For example, if a nonexistent table is specified as part of a table-mode Export, then the Export utility exports all other tables. Then it issues a warning and terminates successfully.

Nonrecoverable Error Messages

Some errors are nonrecoverable and terminate the Export session. These errors typically occur because of an internal problem or because a resource, such as memory, is not available or has been exhausted. For example, if the catexp.sql script is not executed, then Export issues the following nonrecoverable error message:

EXP-00024: Export views not installed, please notify your DBA

Completion Messages

When an export completes without errors, a message to that effect is displayed, for example:

Export terminated successfully without warnings

If one or more recoverable errors occurs but the job continues to completion, then a message similar to the following is displayed:

Export terminated successfully with warnings

If a nonrecoverable error occurs, then the job terminates immediately and displays a message stating so, for example:

Export terminated unsuccessfully

Security Considerations for Direct Path Exports

Oracle Virtual Private Database (VPD) and Oracle Label Security are not enforced during direct path Exports.

The following users are exempt from Virtual Private Database and Oracle Label Security enforcement regardless of the export mode, application, or utility used to extract data from the database:

• The database user SYS

• Database users granted the EXEMPT ACCESS POLICY privilege, either directly or through a database role

This means that any user who is granted the EXEMPT ACCESS POLICY privilege is completely exempt from enforcement of VPD and Oracle Label Security. This is a powerful privilege and should be carefully managed. This privilege does not affect the enforcement of traditional object privileges such as SELECT, INSERT, UPDATE, and DELETE. These privileges are enforced even if a user has been granted the EXEMPT ACCESS POLICY privilege.

Performance Considerations for Direct Path Exports

You may be able to improve performance by increasing the value of the RECORDLENGTH parameter when you invoke a direct path Export. Your exact performance gain depends upon the following factors:

• DB_BLOCK_SIZE

• The types of columns in your table

• Your I/O layout (The drive receiving the export file should be separate from the disk drive where the database files reside.)

The following values are generally recommended for RECORDLENGTH:

• Multiples of the file system I/O block size

• Multiples of DB_BLOCK_SIZE

An export file that is created using direct path Export will take the same amount of time to import as an export file created using conventional path Export.

Restrictions for Direct Path Exports

Keep the following restrictions in mind when you are using direct path mode:

• To invoke a direct path Export, you must use either the command-line method or a parameter file. You cannot invoke a direct path Export using the interactive method.

• The Export parameter BUFFER applies only to conventional path Exports. For direct path Export, use the RECORDLENGTH parameter to specify the size of the buffer that Export uses for writing to the export file.

• You cannot use direct path when exporting in tablespace mode (TRANSPORT_TABLESPACES=Y).

• The QUERY parameter cannot be specified in a direct path Export.

• A direct path Export can only export data when the NLS_LANG environment variable of the session invoking the export equals the database character set. If NLS_LANG is not set or if it is different than the database character set, then a warning is displayed and the export is discontinued. The default value for the NLS_LANG environment variable is AMERICAN_AMERICA.US7ASCII.

Transporting Export Files Across a Network

Because the export file is in binary format, use a protocol that supports binary transfers to prevent corruption of the file when you transfer it across a network. For example, use FTP or a similar file transfer protocol to transmit the file in binary mode. Transmitting export files in character mode causes errors when the file is imported.

Exporting with Oracle Net

With Oracle Net, you can perform exports over a network. For example, if you run Export locally, then you can write data from a remote Oracle database into a local export file.

To use Export with Oracle Net, include the connection qualifier string @connect_string when entering the username and password in the exp command. For the exact syntax of this clause, see the user's guide for your Oracle Net protocol.

User Data

The Export utility always exports user data, including Unicode data, in the character sets of the Export server. (Character sets are specified at database creation.) If the character sets of the source database are different than the character sets of the import database, then a single conversion is performed to automatically convert the data to the character sets of the Import server.

CREATE TABLE partlist 
   ( 
   part     VARCHAR2(10), 
   partno   NUMBER(2) 
   ) 
PARTITION BY RANGE (part) 
  ( 
  PARTITION part_low VALUES LESS THAN ('Z') 
    TABLESPACE tbs_1, 
  PARTITION part_mid VALUES LESS THAN ('z') 
    TABLESPACE tbs_2, 
  PARTITION part_high VALUES LESS THAN (MAXVALUE) 
    TABLESPACE tbs_3 
  );

Data Definition Language (DDL)

Up to three character set conversions may be required for data definition language (DDL) during an export/import operation:

1. Export writes export files using the character set specified in the NLS_LANG environment variable for the user session. A character set conversion is performed if the value of NLS_LANG differs from the database character set.

2. If the export file's character set is different than the import user session character set, then Import converts the character set to its user session character set. Import can only perform this conversion for single-byte character sets. This means that for multibyte character sets, the import file's character set must be identical to the export file's character set.

3. A final character set conversion may be performed if the target database's character set is different from the character set used by the import user session.

To minimize data loss due to character set conversions, ensure that the export database, the export user session, the import user session, and the import database all use the same character set.

Single-Byte Character Sets and Export and Import

Some 8-bit characters can be lost (that is, converted to 7-bit equivalents) when you import an 8-bit character set export file. This occurs if the system on which the import occurs has a native 7-bit character set, or the NLS_LANG operating system environment variable is set to a 7-bit character set. Most often, this is apparent when accented characters lose the accent mark.

To avoid this unwanted conversion, you can set the NLS_LANG operating system environment variable to be that of the export file character set.

Multibyte Character Sets and Export and Import

During character set conversion, any characters in the export file that have no equivalent in the target character set are replaced with a default character. (The default character is defined by the target character set.) To guarantee 100% conversion, the target character set must be a superset (or equivalent) of the source character set.

Exporting Sequences

If transactions continue to access sequence numbers during an export, then sequence numbers might be skipped. The best way to ensure that sequence numbers are not skipped is to ensure that the sequences are not accessed during the export.

Sequence numbers can be skipped only when cached sequence numbers are in use. When a cache of sequence numbers has been allocated, they are available for use in the current database. The exported value is the next sequence number (after the cached values). Sequence numbers that are cached, but unused, are lost when the sequence is imported.

Exporting LONG and LOB Datatypes

On export, LONG datatypes are fetched in sections. However, enough memory must be available to hold all of the contents of each row, including the LONG data.

LONG columns can be up to 2 gigabytes in length.

All data in a LOB column does not need to be held in memory at the same time. LOB data is loaded and unloaded in sections.

Exporting Foreign Function Libraries

The contents of foreign function libraries are not included in the export file. Instead, only the library specification (name, location) is included in full database mode and user-mode export. You must move the library's executable files and update the library specification if the database is moved to a new location.

Exporting Offline Locally Managed Tablespaces

If the data you are exporting contains offline locally managed tablespaces, then Export will not be able to export the complete tablespace definition and will display an error message. You can still import the data; however, you must create the offline locally managed tablespaces before importing to prevent DDL commands that may reference the missing tablespaces from failing.

Exporting Directory Aliases

Directory alias definitions are included only in a full database mode export. To move a database to a new location, the database administrator must update the directory aliases to point to the new location.

Directory aliases are not included in user-mode or table-mode export. Therefore, you must ensure that the directory alias has been created on the target system before the directory alias is used.

Exporting BFILE Columns and Attributes

The export file does not hold the contents of external files referenced by BFILE columns or attributes. Instead, only the names and directory aliases for files are copied on Export and restored on Import. If you move the database to a location where the old directories cannot be used to access the included files, then the database administrator (DBA) must move the directories containing the specified files to a new location where they can be accessed.

Exporting External Tables

The contents of external tables are not included in the export file. Instead, only the table specification (name, location) is included in full database mode and user-mode export. You must manually move the external data and update the table specification if the database is moved to a new location.

Exporting Object Type Definitions

In all Export modes, the Export utility includes information about object type definitions used by the tables being exported. The information, including object name, object identifier, and object geometry, is needed to verify that the object type on the target system is consistent with the object instances contained in the export file. This ensures that the object types needed by a table are created with the same object identifier at import time.

Note, however, that in table mode, user mode, and tablespace mode, the export file does not include a full object type definition needed by a table if the user running Export does not have execute access to the object type. In this case, only enough information is written to verify that the type exists, with the same object identifier and the same geometry, on the Import target system.

The user must ensure that the proper type definitions exist on the target system, either by working with the DBA to create them, or by importing them from full database mode or user-mode exports performed by the DBA.

It is important to perform a full database mode export regularly to preserve all object type definitions. Alternatively, if object type definitions from different schemas are used, then the DBA should perform a user mode export of the appropriate set of users. For example, if table1 belonging to user scott contains a column on blake's type type1, then the DBA should perform a user mode export of both blake and scott to preserve the type definitions needed by the table.

Exporting Nested Tables

Inner nested table data is exported whenever the outer containing table is exported. Although inner nested tables can be named, they cannot be exported individually.

Exporting Advanced Queue (AQ) Tables

Queues are implemented on tables. The export and import of queues constitutes the export and import of the underlying queue tables and related dictionary tables. You can export and import queues only at queue table granularity.

When you export a queue table, both the table definition information and queue data are exported. Because the queue table data and the table definition is exported, the user is responsible for maintaining application-level data integrity when queue table data is imported.

Exporting Synonyms

You should be cautious when exporting compiled objects that reference a name used as a synonym and as another object. Exporting and importing these objects will force a recompilation that could result in changes to the object definitions.

The following example helps to illustrate this problem:

CREATE PUBLIC SYNONYM emp FOR scott.emp;

CONNECT blake/paper;
CREATE TRIGGER t_emp BEFORE INSERT ON emp BEGIN NULL; END;
CREATE VIEW emp AS SELECT * FROM dual;

If the database in the preceding example were exported, then the reference to emp in the trigger would refer to blake's view rather than to scott's table. This would cause an error when Import tried to reestablish the t_emp trigger.

Possible Export Errors Related to Java Synonyms

If an export operation attempts to export a synonym named DBMS_JAVA when there is no corresponding DBMS_JAVA package or when Java is either not loaded or loaded incorrectly, then the export will terminate unsuccessfully. The error messages that are generated include, but are not limited to, the following: EXP-00008, ORA-00904, and ORA-29516.

If Java is enabled, then ensure that both the DBMS_JAVA synonym and DBMS_JAVA package are created and valid before rerunning the export.

If Java is not enabled, then remove Java-related objects before rerunning the export.

Support for Fine-Grained Access Control

You can export tables with fine-grained access control policies enabled. When doing so, consider the following:

• The user who imports from an export file containing such tables must have the appropriate privileges (specifically, the EXECUTE privilege on the DBMS_RLS package so that the tables' security policies can be reinstated). If a user without the correct privileges attempts to export a table with fine-grained access policies enabled, then only those rows that the exporter is privileged to read will be exported.

• If fine-grained access control is enabled on a SELECT statement, then conventional path Export may not export the entire table because fine-grained access may rewrite the query.

• Only user SYS, or a user with the EXP_FULL_DATABASE role enabled or who has been granted EXEMPT ACCESS POLICY, can perform direct path Exports on tables having fine-grained access control.

Advantages of Partitioning a Migration

Partitioning a migration has the following advantages:

• Time required for the migration may be reduced, because many of the subjobs can be run in parallel.

• The import can start as soon as the first export subjob completes, rather than waiting for the entire export to complete.

Disadvantages of Partitioning a Migration

Partitioning a migration has the following disadvantages:

• The export and import processes become more complex.

• Support of cross-schema references for certain types of objects may be compromised. For example, if a schema contains a table with a foreign key constraint against a table in a different schema, then you may not have the required parent records when you import the table into the dependent schema.

How to Use Export and Import to Partition a Database Migration

To perform a database migration in a partitioned manner, take the following steps:

1. For all top-level metadata in the database, issue the following commands:

   1. exp FILE=full FULL=y CONSTRAINTS=n TRIGGERS=n ROWS=n INDEXES=n

   2. imp FILE=full FULL=y

2. For each scheman in the database, issue the following commands:

   1. exp OWNER=scheman FILE=scheman

   2. imp FILE=scheman FROMUSER=scheman TOUSER=scheman IGNORE=y

All exports can be done in parallel. When the import of full.dmp completes, all remaining imports can also be done in parallel.

Restrictions When Using Different Releases of Export and Import

The following restrictions apply when you are using different releases of Export and Import:

• Export dump files can be read only by the Import utility because they are stored in a special binary format.

• Any export dump file can be imported into a later release of the Oracle database.

• The Import utility cannot read export dump files created by the Export utility of a later maintenance release. For example, a release 9.2 export dump file cannot be imported by a release 9.0.1 Import utility.

• Whenever a lower version of the Export utility runs with a later release of the Oracle database, categories of database objects that did not exist in the earlier release are excluded from the export.

• Export files generated by Oracle9i Export, either direct path or conventional path, are incompatible with earlier releases of Import and can be imported only with Oracle9i Import. When backward compatibility is an issue, use the earlier release or version of the Export utility against the Oracle9i database.

Examples of Using Different Releases of Export and Import

Table 21-5 shows some examples of which Export and Import releases to use when moving data between different releases of the Oracle database.

Table 21-5 covers moving data only between the original Export and Import utilities. For Oracle Database 10g release 1 (10.1) or higher, Oracle recommends the Data Pump Export and Import utilities in most cases because these utilities provide greatly enhanced performance compared to the original Export and Import utilities.