flowN for parallel processing in BPEL

Recently I came across a requirement where I had to implement parallel processing in my BPEL. Basically had to post some data to SAP system and was asked to work with multiple connections to increase the throughput. FlowN activity is ideal for this scenario as I had to perform similar processing on different messages/payload. Also this gave me the flexibility to increase the number of parallel flows incase a higher throughput was desired later without making any change to code (set the number of flows desired as a BPEL preference and assign the same to the FlowN variable).

However I did one mistake, which was not creating a Scope inside FlowN and have the variables defined locally inside that scope. When FlowN gets executed this scope should be processed parallely but with different message/payload based on the IndexVariable. Since I had declared the variables globally so at runtime it wasn't executing the parallel flows correctly and always used the payload/message of 1st flow.

<assign name="Set_Counter">
  <copy>
     <from expression="ora:getPreference('NumberOfFlows')"/>
        <to variable="NumOfFlowsToBeProcessed"/>
    </copy>
</assign>

<bpelx:flowN name="Parallel_Flow"
  N="bpws:getVariableData('NumOfFlowsToBeProcessed')"
  indexVariable="Parallel_Flow_Variable">
   <scope name="FlowN_Scope">
       <variables>
           <variable name="Invoke_WS_InputVariable"/>
              ...
       </variables>       
  <sequence name="Sequence_1">
           <assign name="Assign_Input">
               <copy>
                 <from variable="Fetch_Variable"
                   part="part1"
                   query="/ns1:ListOfData/ns1:Data[$Parallel_Flow_Variable]/ns1:name"/>
                  <to variable="Invoke_WS_InputVariable"
                   part="payload"
                   query="/ns2:DataList/ns2:Data/ns2:name"/>
                </copy>

Correct usage is as shown in above code snippet. Using local variables inside the FlowN scope should allow the parallel flows to execute correctly.

A nice read about True Parallelism in BPEL FlowN activity.
true-parallellism-of-the-oracle-bpel-pm-flow-activity