Issue/Introduction:
The SOCKS gateway health check on the downstream ProxySG generates entries in the access log on the SOCKS upstream ProxySG. Because this happens every 10 seconds, it bloats the logs with messages similar to 2013-10-04 11:23:03 1 192.168.50.151 0 FAILED 0 0 unknown - - 0 / - - - - - - - - DENIED "unavailable" - 192.168.100.23.
Resolution:
This type of logging to the upstream ProxySG is intentional and by design.