in the first step request your DBA to clone the schemas from 10.5 to new ones for 10.11.
Then execute the DB configurator to migrate the schemas from 10.5 to 10.11
In the last step you can install and configure IS and MWS to the new schemas by selecting the “side-by-side” migration option.
After installation is completed run the migrate scripts for each instance.
You can find further informations in the webMethods Product Upgrade Guide.