Why is the Planning Portal removing supporting documents?

On average over 1,000 applications are submitted to the Planning Portal every day. This puts significant strain on our system storage. The Planning Portal’s storage facility fills up very quickly given the number of applications being submitted to us. If this reaches capacity and we don’t free up space it will not be possible for new applications to be submitted to local planning authorities via the Planning Portal. Therefore we need to make way for new applications by archiving old attachments. The attachments are stored on an encrypted external storage device.