36 Exporting and Importing XMLType Tables

Overview of Oracle Data Pump

Oracle Data Pump technology enables high-speed movement of data and metadata from one database to another. Oracle Data Pump has two command-line clients, expdp and impdp, that invoke Data Pump Export utility and Data Pump Import utility, respectively. The expdp and impdp clients use procedures provided in PL/SQL package DBMS_DATAPUMP to execute export and import commands, passing the parameters entered at the command-line. These parameters enable the exporting and importing of data and metadata for a complete database or subsets of a database.

The Data Pump Export and Import utilities (invoked with commands expdp and impdp, respectively) have a similar look and feel to the original Export (exp) and Import (imp) utilities, but they are completely separate.

Data Pump Export utility (invoked with expdp) unloads data and metadata into a set of operating system files called a dump file set. The dump file set can be imported only by the Data Pump Import utility (invoked with impdp).

EXPORT/IMPORT Support in Oracle XML DB

Oracle XML DB supports export and import of XMLType tables and columns that store XML data.

You can export and import this data regardless of the XMLType storage format (structured, unstructured, or binary XML). However, Data Pump exports and imports XML data as text or binary XML data only. The underlying object-relational tables and columns used for structured storage of XMLType are thus not exported. Instead, they are converted to binary form and then exported as self-describing binary XML data. XMLType data stored as CLOB instances (unstructured storage) is exported as text.

Regardless of the export format, the format of the dump file is either CLOB or self-describing binary XML with a token map preamble. How Oracle Data Pump stores this data in the dump file depends on the value of the export parameter, data_options (the only valid value for this parameter is xml_clobs.) If you specify this value on the export command line, all XMLType data is stored in text format in the dump file. If you do not specify the xml_clobs parameter in the expdp command, then the format of the XMLType columns in the table determines the format of the data in the dump file. Table 36-1 shows the format of the XMLType columns in the table with the corresponding format of the dump file.

Since XMLType data is exported and imported as XML data, the source and target databases can use different XMLType storage models for that data. You can export data from a database that stores XMLType data one way and import it into a database that stores XMLType data a different way.

Exporting XML Schema-Based XMLType Tables

You can export XMLType tables, whether they are XML schema-based or not. If a table is XML schema-based, then it depends on the XML schema used to define its data. This XML schema can also have dependencies on SQL object types that are used to store the data, in the case of structured storage. Therefore, exporting a user who has XML schema-based XMLType tables also exports the following:

• SQL objects types (if structured storage was used)

• XML schemas

• XML tables

Exporting Hierarchy-Enabled (Repository) Tables

The following guidelines apply to exporting hierarchy-enabled tables, that is, tables that underlie Oracle XML DB Repository data:

• The row-level security (RLS) policies and path-index triggers are not exported for hierarchy-enabled tables. When these tables are imported, they are not hierarchy-enabled.

• Hidden columns ACLOID and OWNERID are not exported for these tables. In an imported database the values of these columns could be different, so they should be reinitialized.

Exporting and Importing Transportable Tablespaces

Using the transportable tablespace feature, you can move a set of tablespaces from one Oracle database to another, whether it is XML schema-based or non-schema-based. When you export using transportable tablespaces mode, only the metadata for tables (and their dependent objects) within a specified set of tablespaces are unloaded. You can then copy the tablespace data files to another Oracle database and perform a transport tablespace import. This is generally very fast, because it involves only copying the tablespace and re-creating the tablespace metadata.

Use TRANSPORT_TABLESPACES parameter in expdp to specify a list of tablespace names for which the object metadata is to be exported from the source database to the target database.

You cannot export transportable tablespaces and import them to a database at a lower release level. The target database must be at the same or higher release level as the source database.

When exporting, Oracle XML DB Repository hierarchy information is lost (see "Exporting Hierarchy-Enabled (Repository) Tables"). When importing, any XML schemas referenced by the data to be imported are also imported.

Repository Resources and Foldering Support

Oracle XML DB supports a foldering mechanism that helps store content in the database in hierarchical structures, as opposed to traditional relational database structures. Foldering lets you use path names and URIs to refer to data (repository resources), rather than table names, column names, and so on. This foldering mechanism is not entirely supported using expdp or impdp.

However, for resources based on a registered XML schema, the XMLType tables storing the data can be exported and imported. During export, only the XML data is exported, the relationship in the Oracle XML DB foldering hierarchy is lost.

Export/Import Syntax and Examples

Export and import using Oracle Data Pump is described in Oracle Database Utilities. This section includes additional guidelines and examples for using commands expdp and impdp with XMLType data. For tables with XMLType data stored as CLOB, Oracle Data Pump exports and imports the tables in the same way as it would do for any table.

The examples presented here use the command-line commands expdp and impdp. After submitting such a command with a user name and command parameters, you are prompted for a password. The examples here do not show this prompting.

expdp system directory=dpump_dir dumpfile=foo.dmp tables=foo 

impdp system tables=foo directory=dpump_dir dumpfile=foo.dmp table_exists_action=append

CREATE TABLE po2 (po XMLType)
  XMLTYPE COLUMN po
  XMLSCHEMA "ipo.xsd"
  ELEMENT "purchaseOrder"
  VARRAY po.XMLDATA."items"."item"
    STORE AS TABLE item_oct2 ((PRIMARY KEY(NESTED_TABLE_ID, SYS_NC_ARRAY_INDEX$)))
      NESTED TABLE po.XMLDATA."shippedItems"."item" STORE AS sitem_nt2;

expdp x4a directory=tkxm_xmldir dumpfile=x4a.dmp

impdp x4a directory=tkxm_xmldir dumpfile=x4a.dmp

impdp x4a directory=tkxm_xmldir dumpfile=x4a.dmp remap_schema=x4a:quine