When the Import NETWORK_LINK parameter is used to specify a network link for an import operation, SQL is used to move the data using an INSERT SELECT statement. The SELECT clause retrieves the data from the remote database over the network link. The INSERT clause uses SQL to insert the data into the target database. There are no dump files involved.
When the Export NETWORK_LINK parameter is used to specify a network link for an export operation, the data from the remote database is written to dump files on the target database. (Note that to export from a read-only database, the NETWORK_LINK parameter is required.)
Because the link can identify a remotely networked database, the terms database link and network link are used interchangeably.
Supported Link Types
The following types of database links are supported for use with Data Pump Export and Import:
Public (both public and shared)
Fixed user
Connected user
Unsupported Link Types
The database link type, Current User, is not supported for use with Data Pump Export or Import.
The Export NETWORK_LINK parameter for information about performing exports over a database link
The Import NETWORK_LINK parameter for information about performing imports over a database link
Oracle Database Administrator's Guide for information about creating database links and the different types of links