The optimizer determines the cost of a table scan as a first step. It also displays the caches used by the table, the availability of large I/O, and the cache replacement strategy.
The following output shows the base cost for the titles table:
Table scan cost is 5000 rows, 748 pages, using data prefetch (size 16K I/O), in data cache ’default data cache’ (cacheid 0) with LRU replacement
If the cache used by the query has only a 2K pool, the prefetch message is replace by:
using no data prefetch (size 2K I/O)