Database Link

When the downstream database is configured, it can be configured to have a database link to the source database. Though the database link creation between the downstream database and the source database is optional, there are many advantages to having one.  The database link name and global name of the source database need to match.

Such a database link simplifies the creation and administration of a downstream Capture process. The DBA can specify that a downstream Capture process use a database link by setting the use_database_link parameter to TRUE when the create_capture or alter_capture is run on the downstream Capture process.

When the database link to the source database exists, certain administrative actions are automatically performed. For instance, the following actions are possible with a database link to the source database:

• It can run the dbms_capture_adm.build procedure at the source database to extract the data dictionary at the source database to the redo log when a Capture process is created.
   

• It can prepare source database objects for instantiation.
   

• It can obtain the first SCN for the downstream Capture process if the first SCN is not specified during the Capture process creation. The first SCN is needed to create a Capture process.

When there is no database link, the above actions need to be done manually.