I have a WebSphere MQ FTE file to queue transfer in which I am splitting a file to multiple messages using delimiter, when I check messages on queue all messages share same WebSphere MQ group ID. Now my problem is when I try to write those messages back to file, instead of creating multiple files fte create only one file with all messages.
What you are trying to do is not possible with WebSphere MQ FTE. When performing a file-to-message transfer, all the messages will have the same group id (as you observe). This is mentioned in the WebSphere MQ FTE Infocenter here:
http://pic.dhe.ibm.com/infocenter/wmqfte/v7r0/topic/com.ibm.wmqfte.doc/f2m_simple_split_delim.htm
Then when you perform a message-to-file transfer, the WebSphere MQ FTE agent will use the message group id field on a transfer to ensure it has consumed all the messages for that transfer. So, on the second stage, all of the messages that were created by splitting a single file are written back to a single file.
I think you will need to raise an RFE (Request for Enhancement) on the IBM DeveloperWorks website for IBM to consider if you require this functionality in WebSphere MQ FTe/MFT:
http://pic.dhe.ibm.com/infocenter/wmqfte/v7r0/topic/com.ibm.wmqfte.doc/resource_monitoring.htm