You can observe data cache performance by examining the cache hit ratio, the percentage of page requests that are serviced by the cache.
One hundred percent is outstanding, but implies that your data cache is as large as the data or at least large enough to contain all the pages of your frequently used tables and indexes.
A low percentage of cache hits indicates that the cache may be too small for the current application load. Very large tables with random page access generally show a low cache hit ratio.
