Selecting a Cache Size
For most environments, the default settings are adequate. However, you might need to increase the cache size if your Broker Server receives very large guaranteed documents or if it receives many guaranteed docs simultaneously.
If you modify the cache setting, keep the following points in mind:
A cache that is too large relative to the amount of physical memory on the
Broker Server host machine might, when full, cause volatile data to begin paging to virtual storage.
A cache that is sized too small reduces performance by increasing the percentage of guaranteed documents that
Broker Server has to fetch from disk.
Always select a cache size that leaves an ample amount of physical memory for the storage of volatile documents and destroy-on-disconnect client information.
The right cache size is highly dependent on the characteristics of the traffic that it will receive. It it affected by factors such as the ratio of volatile to guaranteed documents, document size, arrival rate, and retrieval rate.
You will need to experiment to find a cache setting that suits your mix of documents. In general, larger cache settings are effective if your guaranteed documents are short-lived, meaning that subscribers will retrieve the documents promptly after they are published. For this case, you might even maintain a cache as large as your log file. If, on the other hand, guaranteed documents are likely to remain on Broker Server for lengthy periods before being retrieved, a small cache is generally more practical.