This buffer save retains the head buffers of PIUs that arrive out of sequence on a virtual route. It provides important information contained in the head buffers of the first PIU that is out of sequence and the next 10 PIUs. These buffers are placed on an A-chain for easy access. Use these buffers to determine which product and module caused the PIUs to go out of sequence. If the virtual route is deactivated and reactivated or if a PIU is received in sequence after the 11th head buffer is saved on the A-chain, the head buffers on the A-chain are released.