Recently upgraded to 42.1 from 13.1. while trying to update encountered with error message connection to source lost. Retry option works for some time and after downloading two or three files the same error is encountered. Retry option is to be applied many times to finish security update. I have no problem with Internet browsing using Firefox or Chrome. The problem is repeated when trying update using yast, terminal or apper. I am using from India. Can I change the update mirror to solve the problem.
Yes, you can;
Yast - Software - Software Repositories
Click the Update repo and change the URL to a chosen mirror
Mirrors for OSS are found here
http://download.opensuse.org/update/leap/42.1/oss/openSUSE:Leap:42.1:Update.repo.mirrorlist
Mirrors for NonOSS are found here
http://download.opensuse.org/update/leap/42.1/non-oss/openSUSE:Leap:42.1:NonFree:Update.repo.mirrorlist