The user authorization cache is most efficient when:
If these factors are not met, the efficiency of the User Authorization cache is reduced.
Example: the user authorization cache and agents configured to roundrobin load balance
The more Policy Servers that are in the SiteMinder agent roundrobin pool, the greater the chance that the efficiency of the user authorization cache is reduced.
If a single Web Agent is configured to roundrobin between two Policy Servers, the first request for a protected resource results in a user authorization cache entry on one of the Policy Servers. There is approximately a 50 percent chance that the Policy Server that does not have the cache entry must service the second request. Moving forward, however, both Policy Servers have cached the data for subsequent requests.
Consider now, the effect of a single Web Agent configured to roundrobin between 10 Policy Servers. After a Policy Server authorizes a user and enters the result in to the authorization cache, there is only a 10 percent chance that the same Policy Server services the next request. In this configuration, 5 cache misses must occur before there is a 50 percent chance of a cache hit.
Note: Policy Server clusters can reduce the effect roundrobin load balancing has on the user authorization cache.
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