public void setOverrideStrategy(String overrideStrategy) {
    this.overrideStrategy = overrideStrategy;
  }
When specified under the "settings" section, it allows Ambari to overwrite existing repos stored
in the metainfo table in the Ambari server database.
Two override strategies
ALWAYS_APPLY will override the existing repo. If repo does not exists, add it.
APPLY_WHEN_MISSING will only add the repo info to the table if there is no such entries yet.

  <pre>
    {@code
      "settings" : [
      {
           "repository_settings" : [
           {
             "override_strategy":"ALWAYS_APPLY",
             "operating_system":"redhat7",
             "repo_id":"HDP-2.6",
             "base_url":"http://s3.amazonaws.com/dev.hortonworks.com/HDP/centos7/2.x/BUILDS/2.6.0.3-8"
           },
           {
             "override_strategy":"APPLY_WHEN_MISSING",
             "operating_system":"redhat7",
             "repo_id": "HDP-UTILS-1.1.0.21",
             "repo_name": "HDP-UTILS",
             "base_url": "http://public-repo-1.hortonworks.com/HDP-UTILS-1.1.0.21/repos/centos7"
           }
         ]
      }]
    }
  </pre>
ambari-server/src/main/java/org/apache/ambari/server/topology/RepositorySetting.java