Venu,
Please refer the link below which explains the reasoning for using distribution definition.
https://help.sap.com/saphelp_scm50/helpdata/en/ab/4f6c39c71c0324e10000000a114084/content.htm
After you maintain this setting, I guess the system will not automatically make the sales order reappear. Please run CFM1 / CFM2 to send the sales order again.
Regards
AK