recommended RAM requirement for multi-tier production server.

[SGD]

Hi,

We are planning to setup our production environment with 3 tier of Cognos application.

However, we are confused to determine the optimum or recommended RAM size requirement for our production server because RAM memory requirements depend on the type of processing, the volume of parallel processing, the size and number of simultaneously running reports, schedules, and the memory requirements of the operating system and other applications (such as relational databases).

The minimum amount of memory for installing Cognos is 2GB per Cognos Installation guide and http://publib.boulder.ibm.com/infocenter/c8bi/v8r4m0/index.jsp?topic=/com.ibm.swg.im.cognos.inst_cr_winux.8.4.1.doc/inst_cr_winux_id1727VerifySystemRequirements.html

Below is high level system requirement of our production server:
Processor: Quad core
OS: WIN 2003 64 bit
Cognos: IBM Cognos 8.4.1 (3 tier) 32 bit
Database: Oracle 11g 64 bit
Other software on the same server: none
Performance requirements: High
the number of concurrent clients that access server: 0 to 80

It would be appreciated if someone can guide me to anticipate how much optimum RAM can we apply to our Cognos production server.

Thanks in advance.