Hi Akshant -
Is it standard IDoc or custom Idoc ?
I assume your case might be you may be processing an custom Idoc to post data to a custom table and upon update you may need a outbound idoc to the other system.
If this is the case then while processing the Idoc to update the data in custom table you need take care upon successful update. You can use FM 'MASTER_IDOC_DISTRIBUTE to create outbound IDocs. In that case also you need to populate the Idoc - Control segments ( reading the control records EDIDC data of existing IDOc against which you will create the IDoc) and Data Segments (you need write your logic).
Inbound IDoc get processed through a function module. Inside the same function module you can either call another function module / write to populate the segments of Outbound function module as mentioned above and create the outbound Idoc using 'MASTER_IDOC_DISTRIBUTE'.
If standard idoc, please provide the details.
Regards,
Atul Mohanty