cascading replication & data guard switchover

Hi,

We use Materialized Views to implement replication. A is the center RAC database, several B are A's read-only Materialized Views sites. Some Materialized Views are very big, so we need use Offline Instantiation to create them or complete refresh. All A and B are very critical 7*24 system. Any recreation of Materialized Views is a disaster. Now, for network limit, new sites can't connect to A directly. So I design C to be B's read-only Materialized Views site, and then sync with A indirectly.

My questions are:
1. cascading replication cause weak replication or not? In past years, a B disconnect with A, and then A's Materialized View log become so huge that B can't do fast refresh. The result is we recreate mviews in B, take downtime on the master table and truncate mview log in A. I worry about in cascading replication one site network failure will cause more fix work.

2. If A has a data guard database G, when A switchover to G with no-data loss, whether it will affect B's mviews refresh. Does any one have this kind of experience? I know Oracle use internal trigger for mview, so I worry about whether this objects will be applied in G.

3. Application sometimes need to modify the master table in A. If I don't want to recreate mviews or change mview to advanced replication, Is there any internal way to modify mview's trigger, etc. to propagate DDL changes, like DBMS_REPCAT.EXECUTE_DDL procedure does?

Best Regards,  

Tina

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