In a default Oracle UCM / ORACLE URM instalation only the Title and Date fields are sortable (Click on header to change order).
How do I include a custom field that is sortable on the search result ?
Here's some instructions from Kyle's Blog on WebCenter Content:
In order to add additional fields, it takes a simple component that merges a couple of tables into the standard search definitions tables. Those two additional tables are SearchEngineRules and SearchFieldInfo.
In the custom SearchEngineRules table, you want to add the additional fields to the pipe delimited list of sort fields.