Apply Process Creation

Once the events and messages are propagated to the destination queue, they are ready to be dequeue by the Apply process. The active Apply process applies the changes to the destination objects.

As shown in Figure 5.2, When an Apply process is created using add_subset_rules, add_table_rules, add_schema_rules, or add_global_rules procedures of the dbms_streams_adm package, the Apply process applies only the captured events. When an Apply process is created using the add_message_rule procedure of the dbms_streams_adm package, the Apply process applies only user-enqueued events.

However, when an Apply process is created using the create_apply procedure in the dbms_apply_adm package, the apply_captured parameter can be used to specify whether the Apply process applies captured or user-enqueued events. By default, the apply_captured parameter is set to FALSE for an Apply process created with this procedure. Therefore, by default, an Apply process created with the create_apply procedure in the dbms_apply_adm package applies user-enqueued events. 

Figure 5.2 Apply Process Creation Procedures

 

The next section will provide details on how to create an Apply process and the associated rules using the various methods available.

Using add_table_rules

This is the simplest of all methods and it provides a way to define Apply rules table-by-table at the destination database and helps in the creation of the Apply process. In a single procedural call, all the necessary rules are defined for the Apply process.