GCS/GES Messages Sent - number of messages sent to remote instances over the hardware interconnect. This statistics generally represents overhead caused by functioning of RAC services. This is statistic is a sum of another two statistics:
GCS/GES messages sent = gcs messages sent + ges messages sent
gcs messages received - number of message received by GCS (Global Cache Service). This statistics is derived from v$sysstat.VALUE 'gcs messages sent'.
ges messages received - number of message received by GES (Global Enqueue Service). This statistics is derived from v$sysstat.VALUE 'ges messages sent'.