A well thought out search functionality can greatly enhance the experience. Instead of just thinking about search as a filter criterion, think of this as an alternative and much quicker way to navigate.
Search should not be limited to a single tab or menu item e.g. if you are under the Orders tab then usually you would only be allowed to search for all orders by certain attributes. Having that capability is good, but what if the end-user wants to search for a customer from that location or any comments where a particular customer is mentioned. Think of this as the search your operating system (OS) provides, you can type anything in the search field and then the OS will look for matching filenames, text within files, emails, conversations etc. The figure below gives an example.
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