Regarding Error: Unable to Convert Sender System to ALE Logical System

Question

Hi friends,
in File to IDoc scenario, i created a sender business system called bs_filetoidoc_send based on Standalone technical system and a receiver business system based on ABAP r/3 system. in my SAP IDES system which is dual stack (abap+java), XI client is 001 (LS: devclnt001) and r/3 client is 800 (LS: t90clnt090) i.e i'm posting idoc to t90clnt090.
I tried to send a text file. but while processing xml message in XI, i got an error saying "Unable to Convert Sender System to ALE Logical System".
then i searched the blogs and forum and found the solution. it was saying LS name was not assigned to BS bs_filetoidoc_send. so i went to SLD and tried to assign LS devclnt001 to my sender BS  bs_filetoidoc_send, but got an error saying that "A business system with LS devclnt001 already exists". when i checked which is that BS, it is supposed to be the INTEGRATION SERVER itself with BS name INTEGRATION_SERVER_DEV.
then i configured my sender BS as INTEGRATION_SERVER_DEV itself which picked up the text file successfully and also receiver abap server received the IDOC with correct data and format with status 51. so scenario worked fine when i used my sender BS as INTEGRATION SERVER itself.
please clear my following doubts which arose after this scenario.
1) why the scenario didn't work when I used only standalone sender business system?
2) why should we assign a LS name of XI server to sender business system only in this scenario?
scenario worked according to my requirement, but using integration server itself as a sender BS confused though.
Many Thanks.

Answer 1

1) I can create any no of LS names using SALE
Yes you can create.
> 2) But I can assign a client to any one of those LS names (or 1 client will have only one LS name associated with it)
    One Client will have one LS associated to it...and that can be any one of the LS..created.. use SCC4 to find the associated Ls for all the clients of a system
3) So anyways INTEGRATION_SERVER_DEV has to associated with the client 001 only, so finally I have to use  INTEGRATION_SERVER_DEV only as my sender BS. Probleum is that I can't remove the LS name DEVCLNT001 from INTEGRATION_SERVER_DEV and assign it to bs_filetoidoc_send BS right. If I do so, I think I would get an error saying that INTEGRATION_SERVER_DEV is not associated with the LS name of client 001.
As the logical system defined in Partner profile is expected to arrive in Control record of IDoc..it should be passed in that...
Did u checked this blog../people/rajeshkumar.pasupula/blog/2009/03/16/unable-to-convert-the-sender-service-to-an-ale-logical-system so as per you need the explaination in the blog need to associate the logical system name .
HTH
Rajesh