The data cache is composed of the memory left after SQL Server overhead and the procedure cache memory requirements have been satisfied. The goal is to have enough cache space to hold the majority of all indexes used and a respectable percentage of the most frequently accessed tables, thus reducing physical I/Os.You may also use the DBCC MEMUSAGE statement to view the 20 largest objects in the data cache. Again, you can use this data to determine a respectable size for the data cache based on the sizes indicated for these 20 database objects. You can also determine the size of the most frequently accessed tables and indexes by applying the size formulas given in Appendix A of the Microsoft SQL Server Administrator's Companion. Having calculated these sizes, you may elect to allocate enough memory to SQL Server to contain the entirety of these database objects in the data cache.