Oracle Streams - Dataguard Configuration

Question

Dataguard<------Streams<----Production------> Dataguard
I'm planning to implement a 4-way System where My Production Database with its own Physical Standby will be streaming(Streams database) to A reporting Database with its own Physical Standby.So,Effectively My production database,Especially it's redo logs will be put under severe load.I would like get some light on the feasibility of such a Setup.What parameters can i Take care of so as to make it a profitable High Availability-High Preformance System?
Any suggestions and advice will be highly appreciated..

Answer 1

Remember that Streams check the source DB name of the LCR. Thus the db_name of each standby must be the same as the of the open DB of the remote DB will reject the LCR of the standby when it is activated.
Also streams, dataguard and crash don't fit so well in respect of streams consistency. At the crach time, some transaction will be lost that would have already been sent by streams, since streams react beneath the second. Thus when you activate the dataguard with its loss of some data, you are going to miss some source transaction, that would have already been replicated. You may end with errors on target site, either being dup val on transaction or OLD value in target do not match new value in LCR.
You can't avoid 100% this but you can decrease its extend. Use as method the 'LGW asynct' as dataguard destination.
LOG_ARCHIVE_DEST_2='SERVICE=boston LGWR ASYNC'
http://download.oracle.com/docs/cd/B19306_01/server.102/b14239/log_transport.htm#i1265762
This requires to create the standby redo logs on the dataguard DB (and also on the source DB, since it may becomes itself the standby) so that LGWR updates the remote redo as soon as it can ('async' otherwise 'sync' means that the commit on source is done AFTER the commit into the dataguard and you don't want that).
From my own observation the 'LGWR async nowait' lag usually under 1 sec behind production, which is very good.