How to avoid a function module runnning parallely twice

Question

Hello,
          There is a scenario, where user calls a function module via RFC.
The requirement is to avoid the user from running the function module parallely twice or more because it may lead to dead lock problems.
         To realize this creation of a new enqueue object and set up of enqueue of this object in the function is suggested.
        If the object is blocked (which means the function is already being
running by the sorter), it should go out of the function.
       Can i get help in locking this function module during execution.
With Best Regards,
           Adarsh.

Answer 1

Here's a sample of how you might do this - see comments in code for explanation.. run the program in two differ SAPGui sessions to see the effect.
report zlocal_jc_tfdir_lock.
start-of-selection.                                                   
  perform set_and_check_lock.                                                                               
form set_and_check_lock.                                              
*" Use SAP enqueue to prevent multiple RFC calls of same object       
  data:                                                               
    l_object             like tfdir-funcname.                                                                               
*" Build some name that is specific to your needs                     
*" Include sy-uname in key if lock is per user, not for process                                                                               
concatenate '#Z LOCK:' sy-uname into l_object.                      
*" and enqueue                                                        
  call function 'ENQUEUE_ESFUNCTION'                                  
       exporting                                                      
            funcname       = l_object                                 
       exceptions                                                     
            foreign_lock   = 1                                        
            system_failure = 2                                        
            others         = 3.                                                                               
if not sy-subrc is initial.                                         
    message e398(00)                                                  
      with                                                       
        l_object 'is held by' sy-msgv1 space.                    
  else.                                                          
    write: / l_object, 'is now locked - check sm12 for proof'.   
  endif.                                                                               
endform.