To help Apple improve the quality and performance of Apple’s iOS devices, upon your permission, your iPhone or iPad will routinely send apple diagnostic and usage information. It is likely that you may have seen the option during the initial setup of your iOS device to automatically send diagnostic and usage data to Apple. Most people skim past this option without actually really understanding what it means. The fact that you are sending usage information at time unknowingly sounds scary but it is important to keep in mind that this data that is sent to Apple is anonymous, so you don’t have to worry about privacy if you leave the feature turned on..
Generally speaking, the logs don’t contain any specific app usage data and specific information about the data used within the app — such as what web sites you visited or any personal data entered into the App. The details contained in these logs will include hardware and operating system specifications, performance stats, and data about how a particular app was used (such as where and when). This data is then used by Apple to help research issues and track trends if the need arises.
Over time this constant logging of data can start to take up space on your Apple device. Especially if there is a certain App that is installed that is regularly having issues and crashing. This can be valuable space that you can use for other storage (More important things) such as photos and music. If you find that you are running out of space and you do not understand why then this could be a cause.
How to clear this data
Removing the diagnostic data is as easy as syncing your device to iTunes. Simply just plug your device into your PC or Mac and perform a sync. This can often happen automatically. When syncing your device, it will copy the diagnostic information to iTunes and delete the information from your iOS device.
At the top of your iTunes you will see the Sync status
If you phone does not Sync. Select the sync button and select the Automatically sync when this iPhone is connected
Once transferred, you can find the crash reports on your computer at User-> Your Username -> AppData-> Roaming -> Apple Computer> Library-> Logs -> CrashReporter -> Mobile Device -> Your iPhone, and they can also be viewed in your Console.
How to turn off Apple Diagnostic and Usage
End users can easily opt in and out of diagnostic collection in the Settings → Privacy → Analytics