【IMPDP】实现不同用户之间的数据迁移——REMAP_SCHEMA参数

REMAP_SCHEMA

Default: none

Purpose

Loads all objects from the source schema into a target schema.

Syntax and Description

REMAP_SCHEMA=source_schema:target_schema

Multiple REMAP_SCHEMA lines can be specified, but the source schema must be different for each one. However, different source schemas can map to the same target schema. The mapping may not be 100 percent complete, because there are certain schema references that Import is not capable of finding. For example, Import will not find schema references ××ded within the body of definitions of types, views, procedures, and packages.

If the schema you are remapping to does not already exist, the import operation creates it, provided the dump file set contains the necessary CREATE USER metadata for the source schema and you are importing with enough privileges. For example, the following Export commands would create the dump file sets with the necessary metadata to create a schema, because the user SYSTEM has the necessary privileges:

> expdp SYSTEM/password SCHEMAS=hr
> expdp SYSTEM/password FULL=y

If your dump file set does not contain the metadata necessary to create a schema, or if you do not have privileges, then the target schema must be created before the import operation is performed. This is because the unprivileged dump files do not contain the necessary information for the import to create the schema automatically.

If the import operation does create the schema, then after the import is complete, you must assign it a valid password in order to connect to it. The SQL statement to do this, which requires privileges, is:

SQL> ALTER USER [schema_name] IDENTIFIED BY [new_pswd] 

Restrictions

Unprivileged users can perform. schema remaps only if their schema is the target schema of the remap. (Privileged users can perform. unrestricted schema remaps.)

For example, SCOTT can remap his BLAKE's objects to SCOTT, but SCOTT cannot remap SCOTT's objects to BLAKE.

Example

Suppose that you execute the following Export and Import commands to remap the hr schema into the scott schema:

> expdp SYSTEM/password SCHEMAS=hr DIRECTORY=dpump_dir1 DUMPFILE=hr.dmp

> impdp SYSTEM/password DIRECTORY=dpump_dir1 DUMPFILE=hr.dmp 
REMAP_SCHEMA=hr:scott

In this example, if user scott already exists before the import, then the Import REMAP_SCHEMA command will add objects from the hr schema into the existing scott schema. You can connect to the scott schema after the import by using the existing password (without resetting it).

If user scott does not exist before you execute the import operation, Import automatically creates it with an unusable password. This is possible because the dump file, hr.dmp, was created by SYSTEM, which has the privileges necessary to create a dump file that contains the metadata needed to create a schema. However, you cannot connect to scott on completion of the import, unless you reset the password for scott on the target database after the import completes.