Choosing a Limit Type

After you determine the users and applications to limit, chose the resource limit type.

This table describes the function and scope of each limit type and indicates the tools that help determine whether a particular query might benefit from this type of limit. You may want to create more than one type of limit for a given user and application.

Limit Type	Use for Queries That	Measuring Resource Usage	Scope	Enforced During
io_cost	Require many logical and physical reads.	Use set showplan on before running the query, to display its estimated I/O cost; use set statistics io on to observe the actual I/O cost.	Query	Preexecution or execution
row_count	Return large result sets.	Use the `@@rowcount` global variable to help develop appropriate limits for row count.	Query	Execution
elapsed_time	Take a long time to complete, either because of their own complexity or because of external factors such as server load or waiting for a lock.	Use set statistics time on before running the query, to display elapsed time in milliseconds.	Query batch or transaction	Execution
tempdb_space	Use all space in `tempdb` when creating work or temporary tables.	Number of pages used in `tempdb` per session.	Query batch or transaction	Execution
idle_time	Are inactive.	Time, in seconds, during which the connection is inactive.	Individual processes	Preexecution

The spt_limit_types system table stores information about each limit type.