VERIFIED SOLUTION i

MailStream Plus - Doing REPORT MAILDAT segmented by Batch with multiple Entry points, and getting extra Mail.dat SEG Records.

MailStream Plus™, all versions, all platforms
 
REPORT MAILDAT position 40 has an option 'B' to segment the Mail.dat by Batch (using the B CODE parameter).  
There is also a note in that position of the MailStream Plus™ (MSP) Reference Guide, that if there are multiple entry points, extra SEG records may be produced-
If segmenting by batch and there are multiple entry points, we suggest that you do the following to avoid multiple batch segment breaks by entry points:
• Use SRTFLn parameters to put the batch sort field (002) before the entry point sort field (001).
• Do not use REPORT MAILDAT position 45 to sequence the sort by entry point.


1) 
One possible cause is if the Final Name-Address Output Sequence sort fields start with 001 (entry point), then 002 (batch) like in our default MSP sort.  
When doing Mail.dat Segments by batch, the Output sort sequence needs to have the batch field before entry points.  This would be done by using SRTFLns in the job starting with 002 then 001, etc:
SRTFL1 002 001 ...      

2)
Having an 'E' in REPORT MAILDAT position 45 to 'Define the sort sequence for the output segments and container summaries' as Entry sequence.
That directs MailStream Plus to make SEG breaks on the Entry Points as well as the batches, and causes extra SEG records.
UPDATED:  May 14, 2019