How to make queries on multi provider efficient

1) Always maintian aggregates for the info cubes in the multi provider.

2) Try to use the info object 0INFORPROV and maintain the info cube names ( Usually a query on  multi provider with even 10 cubes uses 1 or 2 info cubes.you cantrace it in ST03N or RSRT)

3) Analyze the query on  multiprovider  through RSRT transaction and use "multi-provider" explain to identify the characteristics on which a logical partition can be made. ( partition can be done by maintianing table "RRKMULTIPROVHINT"

very good article on this :
how to create efficient multiprovider queries

Pointing your SAP BI from one landscape to other

Suppose  you want to copy your productive landscape to a new productive landscape or to change some property of the systems, like hardware, operating system or database. This copy scenario is referred to as "PRD to PRD".
Use this SAP NOTE : 886102 to define new landscape

DEVACCESS table

Sometimes when you try to create a new object. The system might ask for Developer access key. You remember that you've already entered that longtime back. what you can do is search for your developer access key in DEVACCESS table !!