At this stage in capacity planning, you gather information about the level of activity expected on your server, the anticipated number of users, the number of requests, acceptable response time, and preferred hardware configuration. Capacity planning for server hardware should focus on maximum performance requirements and set measurable objectives for capacity.
For your application, take the information that you derive from Examining Results from the Baseline Applications, to see how your application differs from one of the baseline applications. For example, if you are using the HTTPS protocol for a business application similar to MedRec, you should examine the metrics provided for the heavy MedRec application. Perform the same logical process for all of the factors listed in Capacity Planning Factors.
The numbers that you calculate from using one of our sample applications are of course just a rough approximation of what you may see with your application. There is no substitute for benchmarking with the actual production application using production hardware. In particular, your application may reveal subtle contention or other issues not captured by our test applications.
What should I assume about heterogeneous client types? How about programmatic along with HTTP clients? When in doubt, assume the worst. In this case, assume that 100% of the clients will be HTTP clients and develop your capacity planning numbers appropriately.
How do I get my application to run faster? Tune WebLogic Server first, using the BEA WebLogic Server Performance and Tuning, included in BEA Systems documentation. Second, consider using a tuning tool such as jProbe from sitraka at http://www.sitraka.com to find bottlenecks in the code. Also, check the latest in the WebLogic Server documentation and customer support FAQs to see up-to-date application tuning and design guides.
How do I determine how much memory I need? BEA Systems recommends that you install a minimum of 256 MB of memory for each machine running WebLogic Server that will be handling more than minimal capacity. If you are expecting a very heavy load, BEA Systems recommends that you increase your memory substantially.
A WebLogic Server deployment tracks session objects in memory, either to RAM or swapping to disk. There must be sufficient RAM/disk to store all the session objects. This RAM is accessible to Java through the Java heap.
For more information on memory requirements, see BEA WebLogic Server Performance and Tuning.
"Think time" is the time spent by a user between transactions or surfing from one page to another. The BEA capacity planning benchmarks do not account for think time. Rather, the benchmarks send out each subsequent request as soon as the previous one finishes. However, in a real world scenario, a user typically spends a little time between pages.
Given an estimated think time (ETT) in seconds and anticipated transactions per second (TPS) there is a general calculation you can make to estimate the number of concurrent users your system can support: