NFR

Non functional Requirement(NFR):

1. sizing estimatation of app:
register user -> concurrent user -> active concurrent user

a. active concurrent user: one connection to http server and on thread of execution running in app server(1:10 of concurrent user, for OLTP On-Line Transation Processing,it is about 1:5)
b. inactive concurrent user

需要考量的有：
Number of concurrent users(session timeout setting)
Requests per second(CPU load)
Logons per second(CPU sizing of LDAP and DB)


2. Availability = MTBF/(MTBF+MTTR)
MTBF: Mean Time Between Failure
MTTR: Mean Time To Repaire