<p><em>%sn</em> Unique sequence number per log line. Ported from 2.7
<p><em>%<eui</em> EUI logging (EUI-48 / MAC address for IPv4, EUI-64 for IPv6)
Both EUI forms are logged in the same field. Type can be identified by length or byte delimiter.
+ <p><em>%err_code</em> The ID of an error response served by Squid or
+ a similar internal error identifier
+ <p><em>%err_detail</em> Additional err_code-dependent error information.
<tag>memory_pools_limit</tag>
<p>Memory limits have been revised and corrected from 3.1.4 onwards.