Nokia Lumia 930 has an impressive quadcore processor and ran by the well-reviewed Windows Phone 8.1. So, it is expected to run fast and smooth. However, its performance may slow down due to a full storage. Below are the steps from nokia.com for clearing up the memory of your Lumia 930.
To delete unwanted applications go to Settings, tap Storage Sense then swipe the screen to the left. If you want to see the list of apps on your phone, tap details under Apps. Consider the apps that you no longer need and uninstall them to increase the free space in your phone memory. Tap maps under Maps to see the list of maps you have downloaded to your phone. You may delete all the maps at once or individually remove them. Long press an individual map and an option to remove it will po up.
To expunge browsing history, temporary files, cookies and saved passwords in Internet Explorer, go to Settings then applications. Select Internet Explorer then delete history.
To remove previous map searches and temporary files, go to Settings then select applications. Go to maps then delete history.
To delete Bing search history, go to Settings. Select applications. Tap search then delete history.
To remove Office documents, press Start, swipe left, then select Office. Select places or locations then select phone. Long press the document you want to delete then select Delete.
To remove offline mixes from MixRadio, follow the first step in removing Office documents. Then, select MixRadio and go to offline mixes. Long press the mix you want to delete and select Delete.
Clearing up your Lumia 930's storage is important if you want a faster performance or you need a software update.