Hi Nitin
Class CL_XML_DOCUMENT should be useful for your scenario.
You can use the instance method PARSE_XSTRING to read in your XSTRING data into a DOM structure. Subsequently, you can iterate through the nodes to extract the data.
Once you get all your data, you can populate the IDoc data tables then you can execute the usual IDoc FMs to create and/or process the IDoc.
Here are some links on usage of above class.
Visualizing Any Kind of XML Data Using Class CL_XML_DOCUMENT
Upload XML file to internal table - ABAP Development - SCN Wiki
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