can any one please help me to resolve the below issue?

I am trying to write the X12 structure as soon as I populate a record. For e.g. as soon as populating the BEG segment, i am trying to write the segment to file. But the convertToString service is also writing a ST record in addition to the BEG record with the control number.
Please let me know if there is any way to avoid this ST segment being written to file.

Also, would like to know the usage of “Start AT” parameter in the convertToString service.

Appreciate your help in this regard.
Thanks & Regards,

Why do you want to write out the record at once? why not build the entire document list of segments and write out the entire transaction ST to SE?

I have got the usage of the start parameter.