Apache Solr : Error : unknown field _src_

I went through this link and added the code in one of core to upload a multilevel JSON and it worked very well but when I created another core and added same then it is throwing the below error. I spent so much time to solve this error but no luck. The error is,

{{

{ "responseHeader":\{ "status":400, "QTime":93}

, "error":{ "metadata":[ "error-class","org.apache.solr.common.SolrException", "root-error-class","org.apache.solr.common.SolrException"], "msg":"ERROR: [doc=5b62d25] unknown field 'src'", "code":400}} }}

I have added the below code in my solrconfig.xml file.

{{<initParams path="/update/json/docs"> <lst name="defaults"> <!-- this ensures that the entire JSON doc will be stored verbatim into one field -> <str name="srcField">src</str> <!- This means a the uniqueKeyField will be extracted from the fields and all fields go into the 'df' field. In this config df is already configured to be 'text' -> <str name="mapUniqueKeyOnly">true</str> <!- The default search field where all the values are indexed to --> <str name="df">text</str> </lst> </initParams> }}

It means my entire JSON will be stored against the key src.