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在一个时间点，从Server上查询到的系统Session的Wait type 截图
1,CHECKPOINT_QUEUE
Occurs while the checkpoint task is waiting for the next checkpoint request.
Description：This wait type is when the background checkpoint process is idle waiting to be signaled that a new checkpoint request has been entered into the checkpoint queue.
2,LAZYWRITER_SLEEP
Occurs when lazywriter tasks are suspended. This is a measure of the time spent by background tasks that are waiting. Do not consider this state when you are looking for user stalls.
Description：This wait type is when a lazywriter thread is sleeping between checking whether there is pressure on the buffer pool free list requiring buffer being freed (i.e. work for the lazywriter to do). There will generally be a 1 second wait for this type every 1 seconds for each lazywriter thread.
3,DIRTY_PAGE_POLL
Command 是 RECOVERY WRITER
Description：This wait type is when the indirect checkpoint background process is sleeping between polls to discover a dirty page (i.e. a page in the buffer pool that has been modified). From experimentation, there will be one wait occurring every 100ms, with a duration of 100ms.
4,LOGMGR_QUEUE
Occurs while the log writer task waits for work requests.
Description：This wait type is when the log writer thread (or one of the log writer threads, on 2016+) is waiting for something to do (either log to flush or a write to complete).
5，REQUEST_FOR_DEADLOCK_SEARCH
Occurs while the deadlock monitor waits to start the next deadlock search. This wait is expected between deadlock detections, and lengthy total waiting time on this resource does not indicate a problem.
Description：This wait type is when the background deadlock monitor is waiting between deadlock searches. The frequency between searches is usually 5 seconds, but the interval between searches will contract and expand based on how frequently deadlocks are occurring.
6，KSOURCE_WAKEUP
Used by the service control task while waiting for requests from the Service Control Manager. Long waits are expected and do not indicate a problem.
Description: This wait type is when the background control task in SQL Server is waiting to be told to shut the instance down. There will only be one wait of this type, which will show up with a zero wait time in sys.dm_os_wait_stats, but SPID 7 will show this wait type in sys.dm_os_waiting_tasks and sys.dm_exec_requests with an increasing wait time since the instance started.
7，SQLTRACE_INCREMENTAL_FLUSH_SLEEP
Description: This wait type is when a thread is sleeping between checks for SQL Trace information to flush out to a trace file.
参考doc：
sys.dm_os_wait_stats (Transact-SQL)
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原文地址：http://www.cnblogs.com/ljhdo/p/5584959.html
