The cache overhead accounting for Adaptive Server versions
12.5.1 and later is more explicit than earlier versions of Adaptive
Server. The actual overhead is the same, but instead of being part
of the server overhead, it is now considered as part of the cache
overhead.
sp_helpcache can report the amount of overhead required to manage a named data cache of a given size. When you create a named data cache, all the space you request with sp_cacheconfig is made available for cache space. The memory needed for cache management is taken from the global memory block pool.
To see the overhead required for a cache, give the proposed size. You can use P for pages, K for kilobytes, M for megabytes, or G for gigabytes. The following example checks the overhead for 20,000 pages:
sp_helpcache "20000P"
2.96Mb of overhead memory will be needed to manage a cache of size 20000P
You are not wasting any cache space by configuring user caches. Approximately 5 percent of memory is required for the structures that store and track pages in memory, whether you use a single large data cache or several smaller caches.
