As I discussed in an earlier column, SQL Server keeps a plan cached for each query it sees (assuming the query requires planning in the first place, of course). That’s great for speeding up processing the next time that query shows up because the plan for the query can simply be pulled from the cache.
However, there are any number of queries in any application that SQL Server may never see again (at least in, for example, the next 24 hours). The plans for these “one-time” queries are taking up space in the cache even though they might never be used again. The cache manager will recover space if necessary by keeping track of plans with low planning costs and discarding those plans as the cache runs out of space. However, that doesn’t address the space used by those “one-time” plans.
Peter shares a great tool that not only makes your application run faster but gives you insight into other potential problems. That's great for speeding up processing the next time that query shows up because the plan for the query can simply be pulled from the cache.