Geek Sync I Dealing with Bad Roommates - SQL Server Resource Governor

Editor's Notes

• #9: What we did before to control resource usage was inflexible and largely reactive: Kill SPIDs with “runaway” queries utilize SET QUERY_GOVERNOR_COST_LIMIT per query (or per instance with sp_configure) use separate instances with affinity to separate workloads juggle scheduled jobs to avoid peak activity times schedule creation / destruction of procedures or even changing passwords to block certain groups during peak load times
• #12: Classifier function - Return workload name (sysname) Collation sensitive workload name Error assigns DEFAULT group Can’t assign INTERNAL group Must be schema-bound
• #13: xA bucket of “similar” requests (as determined by you). Thing to that your connection has been assigned to after it has been classified.If classifier function does not work, default poolDDL Internal Tasks (Lazy-writer, checkpoint, ghost cleanup) run under internal group. It can pressurize everything else.Default Group has no limit but can get pressurize by everything else.Max Requests. One pool : many groups (no limit) Controls: Importance  (Low, Normal, High) Max Concurrent Requests Request Max CPU Time Seconds Request Max Memory Grant Percent Request Max Memory Grant Timeout Request MAX DOP 
• #15: Please note: Amount of Memory is not what you might think. Its amount of “query execution memory” given to that connection. Its NOT total amount of Server Memory. So you could have a connection that reads a lot of data and uses buffer pool. It doesn’t count of Plan Cache and Bpool.Default and InternalCPU: Amount of CPU is for per scheduler. NOTE:::: If there is no contention you would not see throttling. RG kicks in when there is a need.
• #19: The internal pool represents the resources consumed by the SQL Server itself. This pool always contains only the internal group, and the pool is not alterable in any way. Resource consumption by the internal pool is not restricted. Any workloads in the pool are considered critical for server function, and Resource Governor allows the internal pool to pressure other pools even if it means the violation of limits set for the other pools. In some cases, Resource Governor will act differently than how it is set up. Let’s look at a few of these cases. No resource contention. Although you have set up some limitation to the resources for a particular pool, you might find cases when the limits are not taken into account. Consider a scenario where you have set up a pool with a CPU cap of 25%. If at the time of executing a task in that pool there are no other active or workable SPIDS in other pools, this cap will not be taken into account. Importance. Let’s say you have two tasks: Task A with importance of HIGH, and Task B with importance of LOW. These settings do not mean that Task A will execute first, and then Task B will be executed. Importance is nothing but a numeric weight given to a request. What the importance settings actually do is to tell the scheduler to give 3 out of 4 units of work to Task A and the other one part to Task B. Both tasks can execute simultaneously. Waiting or pre-emptive state. If a query is waiting for other resources such as I/O, another query that has a cap set might use all available resources even though the first task is still active. That is because Resource Governor does not recognize a task that is in a WAITING for resource mode. Off-limit requests. There are quite a few requests that are off limits to Resource Governor. Extended stored procedures, for example, are usually off limits, including Database Mail, linked server queries, and COM/OLE automation.