When an OES 2015 SP1 server is updated properly, the update repository list is refreshed to include Updates entries for your OES 2015 SP1 and SLES 11 versions.
To verify that you have updates from both update repositories:
At a terminal prompt on the server you have updated, enter the following command:
zypper lr
The list of repositories should include update repositories for your SLES 11 and OES 2015 SP1 versions. For example, after updating an OES 2015 SP1 server, the repositories listing should include both SLES11-SP4-Updates and OES2015-SP1-Updates as subscribed update repositories.
After the repository list contains the correct entries, update your server by repeating the pertinent instructions in Section 8.4, Updating the Server.