encodeReferenceToBase64 function failing files more than 10 BM files

Summary

encodeReferenceToBase64 function failing files more than 10 BM files

Content

Quite important requirement as files should be encoded base 64 and pass to other service to attach the files to AR Invoice in Oracle ERP. 
Oracle Docs link 
https://docs.oracle.com/en/cloud/paas/integration-cloud-service/icsug/encoding-attachment-content-base64-string.html

The solution is working fine with smaller sizes like less than 10 MB and the files > 10 are failing with the transformation exceptions, as this is quite important requirement to , how come we can over come the situation of transformation. 

faultName: {{http://schemas.oracle.com/bpel/extension}subLanguageExecutionFault} messageType: {{http://schemas.oracle.com/bpel/extension}RuntimeFaultMessage}