Try to upgrade a SLES12SP2. The host ist registerd to a local SMT(SCC). 'zypper patch' shows that there are no patches to install. But zypper migration brings:

Code:
# zypper se *migration*
Refreshing service 'SMT-http_xxxxxxxxxxx'.
Loading repository data...
Reading installed packages...

S | Name                    | Summary                                | Type
--+-------------------------+----------------------------------------+--------
i | sle12-desktop-migration | Hook to upgrade desktop settings       | package
i | yast2-migration         | YaST2 - Online migration               | package
i | zypper-migration-plugin | Zypper subcommand for online migration | package
#
Code:
# zypper migration

Executing 'zypper  refresh'

Repository 'SLES12-SP2-Pool' is up to date.
Repository 'SLES12-SP2-Updates' is up to date.
Repository 'SUSE-PackageHub-12-SP2-Pool' is up to date.
Repository 'SUSE-PackageHub-12-SP2-Standard-Pool' is up to date.
All repositories have been refreshed.

Executing 'zypper  --no-refresh patch-check --updatestack-only'

Loading repository data...
Reading installed packages...

Considering 0 out of 22 applicable patches:
0 patches needed (0 security patches)

Can't get available migrations from server: SUSE::Connect::ApiError: Not Found
'/usr/lib/zypper/commands/zypper-migration' exited with status 1
#
The SMT-Server has these repos:

Code:
# smt-repos -o | grep SLES12-SP3
| Yes     | 10 | nu   | SLES12-SP3-Debuginfo-Pool            | sle-12-x86_64 | SLES12-SP3-Debuginfo-Pool for sle-12-x86_64            | Yes             | No      |
| Yes     | 11 | nu   | SLES12-SP3-Debuginfo-Updates         | sle-12-x86_64 | SLES12-SP3-Debuginfo-Updates for sle-12-x86_64         | Yes             | No      |
| Yes     | 12 | nu   | SLES12-SP3-Installer-Updates         | sle-12-x86_64 | SLES12-SP3-Installer-Updates for sle-12-x86_64         | Yes             | No      |
| Yes     | 13 | nu   | SLES12-SP3-Pool                      | sle-12-x86_64 | SLES12-SP3-Pool for sle-12-x86_64                      | Yes             | No      |
| Yes     | 14 | nu   | SLES12-SP3-Updates                   | sle-12-x86_64 | SLES12-SP3-Updates for sle-12-x86_64                   | Yes             | No      |
# smt-repos -o | grep SLES12-SP2
| Yes     |  5 | nu   | SLES12-SP2-Debuginfo-Pool            | sle-12-x86_64 | SLES12-SP2-Debuginfo-Pool for sle-12-x86_64            | Yes             | No      |
| Yes     |  6 | nu   | SLES12-SP2-Debuginfo-Updates         | sle-12-x86_64 | SLES12-SP2-Debuginfo-Updates for sle-12-x86_64         | Yes             | No      |
| Yes     |  7 | nu   | SLES12-SP2-Installer-Updates         | sle-12-x86_64 | SLES12-SP2-Installer-Updates for sle-12-x86_64         | Yes             | No      |
| Yes     |  8 | nu   | SLES12-SP2-Pool                      | sle-12-x86_64 | SLES12-SP2-Pool for sle-12-x86_64                      | Yes             | No      |
| Yes     |  9 | nu   | SLES12-SP2-Updates                   | sle-12-x86_64 | SLES12-SP2-Updates for sle-12-x86_64                   | Yes             | No      |
#
What means: Can't get available migrations from server: SUSE::Connect::ApiError: Not Found