ERP Concurrent User Estimator

I found a very interesting spreadsheet called ERP Software Concurrent User Estimator from TGI on this link.

The formula used by them is:

No. of Concurrent Users = (0.3 x Low Activity Users) + (0.6 x Medium Activity Users) + High Activity Users

This is a good estimator which can be used to come up with number of concurrent users, which is needed for sizing an environment.

Calculate number of concurrent users of an existing instance

The view v$license keeps track of concurrent sessions and users.

SQL> desc v$license

 Name                                      Null?    Type

 ----------------------------------------- -------- ----------------

 SESSIONS_MAX                                       NUMBER

 SESSIONS_WARNING                                   NUMBER

 SESSIONS_CURRENT                                   NUMBER

 SESSIONS_HIGHWATER                                 NUMBER

 USERS_MAX                                          NUMBER

 CPU_COUNT_CURRENT                                  NUMBER

 CPU_CORE_COUNT_CURRENT                             NUMBER

 CPU_SOCKET_COUNT_CURRENT                           NUMBER

 CPU_COUNT_HIGHWATER                                NUMBER

 CPU_CORE_COUNT_HIGHWATER                           NUMBER

 CPU_SOCKET_COUNT_HIGHWATER                         NUMBER

select sessions_current from v$license;

The above query will give you the number of concurrent users right now.

You can write a small job which will capture this information every hour for a week.  Once you have this data, you can take an average of this data to get the number of concurrent users.