After extensive analysis, it seems that sqlcmd doesn't manage buffers and transactions properly, and it lead to the error, when there's lot's of data. I wrote my own alternateive program for #SQLCMD using #Python, and now the import was successful. So it turns out that sqlcmd code is just bit bad, and someone had to write better alternative. To be honest, some of the individual insert statements were up to 8 megabytes per row. #SQL