Well below are the meaning of codes used by squid in access.log ,I have posted here as most the time also need them
.. so now other can also benefitted.
TCP_HIT
A valid copy of the requested object was in the cache.
TCP_MISS
The requested object was not in the cache.
TCP_REFRESH_HIT
The requested object was cached but STALE. The IMS query for the object resulted in "304 not modified".
TCP_REF_FAIL_HIT
The requested object was cached but STALE. The IMS query failed and the stale object was delivered.
TCP_REFRESH_MISS
The requested object was cached but STALE. The IMS query returned the new content.
TCP_CLIENT_REFRESH_MISS
The client issued a "no-cache" pragma, or some analogous cache control command along with the request. Thus, the cache has to refetch the object.
TCP_IMS_HIT
The client issued an IMS request for an object which was in the cache and fresh.
TCP_SWAPFAIL_MISS
The object was believed to be in the cache, but could not be accessed.
TCP_NEGATIVE_HIT
Request for a negatively cached object, e.g. "404 not found", for which the cache believes to know that it is inaccessible. Also refer to the explainations for negative_ttl in your squid.conf file.
TCP_MEM_HIT
A valid copy of the requested object was in the cache and it was in memory, thus avoiding disk accesses.
TCP_DENIED
Access was denied for this request.
TCP_OFFLINE_HIT
The requested object was retrieved from the cache during offline mode. The offline mode never validates any object, see offline_mode in squid.conf file.
UDP_HIT
A valid copy of the requested object was in the cache.
UDP_MISS
The requested object is not in this cache.
UDP_DENIED
Access was denied for this request.
UDP_INVALID
An invalid request was received.
UDP_MISS_NOFETCH
During "-Y" startup, or during frequent failures, a cache in hit only mode will return either UDP_HIT or this code. Neighbours will thus only fetch hits.
NONE
Seen with errors and cachemgr requests.
The following codes are no longer available in Squid-2:
ERR_*
Errors are now contained in the status code.
TCP_CLIENT_REFRESH
See: TCP_CLIENT_REFRESH_MISS.
TCP_SWAPFAIL
See: TCP_SWAPFAIL_MISS.
TCP_IMS_MISS
Deleted, TCP_IMS_HIT used instead.
UDP_HIT_OBJ
Hit objects are no longer available.
UDP_RELOADING
See: UDP_MISS_NOFETCH.
If anyone wants to add something then they are most welcome
I mean related to squid codes..
