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.