Report avaibility is impacted due to BIA Indices

Question

Hi BIA experts,
We are going to implement BIA for our BW reports. However, from the information that I gathered, I have a concern in here.
As I know before, when BIA Indices are not available, the report avaibility will not get impacted because it will automatically getting the data from DB (InfoCubes). Unfortunately, this is not the case in real life.
From the information that I gathered from people whom did the BIA implementation before.
When you have started using BIA Indices, when BIA Indices are not available, the reports which are having BIA indices will not be available until we fix the BIA Indices, all or nothing.
I heard there is an option to have DB/Aggregate fallback setting. When BIA indices are not available, DB/Aggregate fallback occured and the report will use aggregate/DB. This DB/aggregate fallback can be automatic or manual turned on.
My questions are:
1. What are the disadvantages using DB/Aggregate fallback setting? Will it impact BIA performance?
2. Except DB/Aggregate fallback, are there any other options to prevent report not available when BIA indices not available? eg. BIA index back-up (if there are such things).
Thank you very much for your response. Really appreciate.
Regards,
Mona

Answer 1

Hi Mona,
When BIA becomes unavailable, the BI system creates an entry(timestamp) to the table called  RSDDTREXHPAFAIL. If you have email address(es) entered to the table called RSDDTREXEMAIL, then it sends an alert to those adresses. When this happens for the next thirty minutes all queries are diverted to BI ( or until you removed the entry from RSDDTREXHPAFAIL). This usually works when some servers become unavailable, and there is no disadvantage(other then not able to use BIA)
The problem here is sometime the system/server(s) hang, when this happens the BI system doesn't know the problem therefore doesn't create an entry. Then the users start receiving BIA errors. To fix this you go to RSDDBIAMON2 to switch the cubes off, yet if the blades are not available this transaction hangs sometime too. So we created adhoc programs to turn the cubes on/off + exclude/include users from BIA + include/exclude queries from BIA + and to create!/delete entries from the RSDDTREXHPAFAIL table.
Cheers
Tansu