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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