After the completion of the implementation if the end user is unable to process a transaction,how do we rectify that?Are the consultants authorized to access the production server?

yes the end user works on production server only, if he get any log in problem ther client technical team will take care

Consultants are authorized to carry out transactions in production server. But it is advisable to use the ID of user facing the problem. The best way to solve a problem related to SD is go to delivery document flow and see the transactions carried out. This helps in quick identification of mistake done by the user.

Yes consultants areauthorized to access the production server. Also training material including the screen shots, possible errors & solutions to them are handed over to the end users. SAP tutor files (known as SIM files) are also provided for the end users so that it will help the users to find the error area and follow the correct path.

On company web sites the training material, solutions to the problems etc support is provided for the end users.

Also end users can make a phone call to the support team members (respected module or functional area) so that the problem can be solved.