January 17, 2008 at 12:27 am
Hi All,
I have been trying to understand the options provided in Proactive caching namely,
Silence interval
Silence override interval
Latency
Bring online immediately and
Enable ROLAP Aggregations.
As far as my understanding goes:
Silence interval: The minimum time server waits after getting a notification from the datasource to start rebuilding the cache. If suppose another request comes with the time of 10 seconds(default silence interval),it will further wait for 10 more seconds minimum before it starts rebuilding the cache.
Silence override interval: This is the maximum time for which the server can be wait after it receives first notification from the datasouce before it starts rebuilding the cache. In the case where there are subsequent data changes in the data source, the notifications after silence override interval are queued and the server starts rebuilding the cache.
Latency: THe maximum time frame for which the Cache and Datasource are apart ie not in sync with each other.
Bring online immediately: If this option is enabled then the user queries are redirected to relational data source, or in other words the server shifts to ROLAP Mode.
Now lets discuss the scenarios(assume MOLAP storage),
1)if suppose a request has come and the silence interval=10sec and silence override interval=10 min, others options are disabled. Then after the first request, server waits for 10 secs and if there are no further notifications within the 10sec timeframe it starts rebuilding the cache.
Now the question is how are user queries answered?
Can somebody also give the answers, if suppose the latency is set to 4 hours and wat is the impact of setting Bring online immediately checked and not checked???
January 31, 2008 at 11:12 pm
If you look at the AS2005 Performance Guide (google showed me a pdf copy here), skip down to page 82 (heading is Availability Settings) you'll see the answer to at least your first question (they hit the old cache until the new one is processed and brought online). It also appears to answer your aecond question - the bring online immediately really relates to when the new cache is being processed, during this time, the server will send user queries directly to the source (ROLAP, as you'd mentioned).
Steve.
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