With Spotlight Search, you can search for data saved on your iPhone, such as contacts, email addresses, calendar entries, song titles and applications. While this feature can be useful, it does require your phone's hard drive to work harder and can slow down its processor speed. If you notice that your iPhone is not performing optimally, you can disable Spotlight Search entirely or just for selected applications.
Click the Settings icon on your iPhone's home screen.
Click "General" in the Settings menu, and select the "Spotlight Search" option. This brings you to the Spotlight Search options for your device.
Disable Spotlight Search by removing the check mark next to each entry in the Spotlight Search menu. You can do this by simply clicking on each individual entry. If there are no check marks visible on the Spotlight Search menu, you have completely disabled the feature.