RFC Resources on the Application Server 
The graphic below shows the SAP application server resources relevant for parallel RFC.
Resources can be assigned from the following areas:
Logging On to the SAP System
A total of rdisp/tm_max_no users can be simultaneously logged on to the server (using the GUI or RFC). If rdisp/rfc_max_login percent of the maximum number of users are logged on, no more RFC logons can be accepted. An RFC user may occupy a maximum of rdisp/rfc_max_own_login percent of the login slots (see isp/tm_max_no).
You can see a user
overview in transaction SM04. For more information, see 
Display and Manage User
Sessions.
RFC Requests in the Dialog Queue
The dialog queue of the dispatcher contains rdisp/elem_per_queue entries. A maximum of rdisp/rfc_max_queue percent of these may be filled by RFC requests.
You can see a
server overview in transaction SM51. For more information, see Overview of SAP Application
Servers.
Entries in the Communication Table
The communication table contains an entry for every CPIC communication for all parties involved. The table can contain a maximum of rdisp/max_comm_entries entries. rdisp/rfc_max_comm_entries percent of these may be occupied by one user.
You can see a
server overview in transaction SM51. For more information, see
Overview of SAP Application
Servers.
Dialog Work Processes
When the server is
started, it has rdisp/wp_no_dia dialog work processes. This
number can, however, be changed while the server is running. One way to do
this is to use operation mode switching. You can find out the current number
of processes in the Process Overview (transaction SM50; see also Display and Control Work
Processes). Of the
dialog work processes, the dispatcher keeps rdisp/rfc_min_wait_dia_wp free for “genuine” dialog
requests (not RFC).
A user may occupy a maximum of rdisp/rfc_max_own_used_wp percent of dialog processes.
The same
parameters are used to control the number of plug-in requests (HTTP or SMTP
requests coming from the ICM) that can be processed at the same time. See
ICM Parameters.
Overview of All RFC Resources in the SAP System
Transaction SARFC is used to monitor the resources on all servers in the SAP system. This is described in the section Monitoring RFC Resources on the Application Server.