QuickSearch is a really useful search tool in UCM because, as the word says, it allow to perform quick searches directly from every content server page just inserting search criteria and not going through the classic search form that searches content by filling certain metadata fields.
By default QuickSearch searches against dDocName, dDocTitle and dDocFullText, if enabled.
If you need to perform searches against other metadata you can easily customize it.
Go to Administration -> Admin Server
Click General Configuration and insert:
QuickSearchFields are metadata fields against which searches are performed.
QuickSearchOperators are matching criteria for searches i.e. matches, hasSubstring.
Please note that every metadata inserted in QuickSearchFields field has corresponding search operator in QuickSearchOperators field.
Once done restart your UCM instance.
If you like you can manually enter these configurations by adding them in /home/oracle/<your_ucm_directory>/cs/config/config.cfg