Questions tagged [wait-types]

Whenever the server is running queries, it’s tracking how much time it spends waiting on bottlenecks. These wait statistics are the easiest way to identify your bottleneck.

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33
votes
1answer
30k views

SLEEP_TASK Wait Type in SQL Server - What does it indicate?

I haven't seen the SLEEP_TASK wait type before, and today I seem to be getting a ton of them. I'm not the official DBA, just a SQL Server developer who knows some DBA stuff. We upgraded our servers ...
16
votes
1answer
21k views

Is ASYNC_NETWORK_IO wait type anything to worry about?

In looking at the list of stored procedures that take long time to execute, one stands out as causing the most wait. However, most of that wait (81%) is ASYNC_NETWORK_IO and I know why: the stored ...
13
votes
3answers
31k views

High CXPACKET and LATCH_EX waits

I am having some performance issues with a data processing system which I am working on. I have gathered wait stats from a one hour peroid which show a large amount of CXPACKET and LATCH_EX wait ...
12
votes
1answer
11k views

Troubleshooting SOS_SCHEDULER_YIELD wait

Running our corporate ERP (Dynamics AX 2012), I noticed our production environment seemed much slower than our development systems. After performing the same activities in both the development and ...
10
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2answers
2k views

LATCH_EX Waits on Resource METADATA_SEQUENCE_GENERATOR

We have a process that generates an inventory report. On the client side, the process splits of a configurable number of worker threads to build a chunk of data for the report that corresponds to one ...
9
votes
3answers
65k views

How to troubleshoot enq: TX - row lock contention?

I have the following situation. I have RAC. On both nodes there are the locks. On the First Node SID EVENT USERNAME BLOCKING_SESSION ROW_WAIT_OBJ# OBJECT_NAME ...
9
votes
1answer
499 views

Blocked sessions waiting with PAGELATCH_* wait types?

Edited : Why are sessions reporting being blocked but waiting with PAGELATCH_*, and not LCK_M_ related wait types? I previously assumed that SQL server would only report blocking sessions in the ...
8
votes
2answers
2k views

Intermittent RESOURCE_SEMAPHORE_QUERY_COMPILE Wait Stats

I'm trying to troubleshoot some intermittent CPU spikes that we're witnessing on one of our production SQL Servers. We're running SQL Server 2008 R2 Standard Edition with 28 GB RAM and 4 CPU cores. ...
8
votes
2answers
2k views

SQL Server performance: PREEMPTIVE_OS_DELETESECURITYCONTEXT dominant wait type

I received a call yesterday from a customer who was complaining about high CPU usage on their SQL Server. We're using SQL Server 2012 64 bit SE. Server is running Windows Server 2008 R2 Standard, 2.20 ...
7
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3answers
17k views

Investigating high SQL waits, especically LCK_M_U

Recently I have been struggling with SQL server performance and although we have fixed a huge multitude of basic errors in the config it is still performing badly. To clarify it is not overall ...
7
votes
1answer
285 views

Disk I/O and PAGEIOLATCH_XX

We have been having CPU issues with one of our servers lately and while we have been looking into this we have also noticed queries running slowly with waits of PAGEIOLATCH_XX. In particular, a ...
6
votes
2answers
396 views

Why would I get PREEMPTIVE_OS_AUTHORIZATIONOPS using tSQLt when Working at Home?

I have an SSDT project containing tSQLt unit tests. I always find when working at home that publishing this and running all tests (from a post deploy script) is problematic (against both localdb and ...
6
votes
1answer
904 views

Attempting to tune a Sharepoint site using SQL Server Waits and Queues

I'm pretty new to this performance tuning with Waits and Queues thing - fascinating, but also not always all that intuitive... Right now, a customer of mine has a SQL Server 2008 64-bit Enterprise ...
6
votes
1answer
205 views

Strange blocking on readable secondary after reboot

We are running an SQL Server 2014 Availability Group with 3 replicas, one synchronous (SQL2 for this matter) and one asynchronous secondary replica. We also configured read-only routing to the ...
6
votes
1answer
2k views

What does the wait type PREEMPTIVE_XE_CALLBACKEXECUTE mean?

I have two instances in the last week where a DROP command for an Extended Events session has taken over a day to complete, sitting with the wait: PREEMPTIVE_XE_CALLBACKEXECUTE. Can anyone explain ...
6
votes
1answer
398 views

SQL Server CLR procedures and SQLCLR_QUANTUM_PUNISHMENT

I have a CLR stored procedure running on SQL Server 2014. This stored procedure gathers some data (generally numbering in the tens-of-thousands of rows range), runs some computations on the data, ...
6
votes
1answer
2k views

How to solve blocking on tempdb

I am having tempdb contention (I guess, at least) on one of the servers (SQL Server 2008 R2). Both the blocker and the waiters (10 of them) has PAGELATCH_EX wait type on database tempdb and all ...
5
votes
2answers
10k views

Huge “Network I/O” type resource waits

We have an in-house application, developed in WinDev, that uses a Microsoft SQL Server 2012 SP2 (build 11.0.5058) database running on Windows Server 2008R2. We are experiencing performance issues. At ...
5
votes
1answer
236 views

Does sys.dm_os_waiting_tasks include RUNNABLE threads?

From MSDN: Returns information about the wait queue of tasks that are waiting on some resource. Is CPU considered a resource in this definition? I initially thought it's not, but what made me ...
5
votes
1answer
2k views

Is the SQLTRACE_FILE_BUFFER wait type documented? What does it indicate?

We run a background task on one of our servers which polls sys.dm_exec_requests for long-running queries, gathering diagnostic information when it finds them, including wait type. I'm seeing a number ...
5
votes
1answer
5k views

What is the Wait Type “QDS_Shutdown_Queue” referring to?

I'm gathering wait types on a load test environment, and the second biggest wait type is QDS_SHUTDOWN_QUEUE. The stats are coming from sys.dm_os_wait_stats, but I can't find any documentation that ...
5
votes
1answer
109 views

Different Disk Drive Same Backend Storage

I have a database running on a VM which is getting hammered during a large load, in particular I can see waits of WRITELOG happening. My initial thought is to split the files out on to their own ...
4
votes
2answers
566 views

Can WAITFOR increase CXPACKET waits?

If I have some T-SQL code like this: While @done<1 Begin WAITFOR DELAY '00:00:30'; Set @done=<some select statement> End Is this likely to increase waits for CXPACKET? Presumably the other ...
4
votes
3answers
370 views

Why is sql server waiting for acknowledgment?

I have an application that often request a big set of rows [about 20K] from a sql view, in the mean time other applications can't update the table from where the data comes from, the update query's ...
4
votes
2answers
918 views

PAGEIOLATCH wait type

I'm trying to get a better understanding of how serious this wait type is. I'm using sp_WhoIsActive stored procedure. Our DBAs don't seem to know much about this wait type. But I often see it when I ...
4
votes
3answers
6k views

PageIOLatch_Sh waits noticed after tuning an index

Lately, a lot of queries to the database are timing out. While investigating I found that queries are in the suspended state with wait_type as PageIOLatch_Sh. I have not noticed so many queries being ...
4
votes
2answers
183 views

CXPACKET wait on SQL Server

Recently I am experiencing performance issue on a SQL Server database and I have two queries that show me the wait as shown below, one of the databases on this server is a member of Always On replica, ...
4
votes
3answers
1k views

Reading ASYNC_NETWORK_IO wait stats

I was troubleshooting some bad performance for a client yesterday and identified that there was a missing index for a particular set of queries that were heavily used (this was for an ERP applicaton: ...
4
votes
1answer
356 views

What is the PREEMPTIVE_REENLIST wait type in Microsoft SQL Server 2008 R2

This is not urgent, just curiosity. QUESTION: I was trying to troubleshoot a slow server today, and I came across a high figure for a wait type called PREEMPTIVE_REENLIST. I'm not able to find this ...
4
votes
2answers
200 views

Help with wait type CHECK_TABLES_THREAD_BARRIER

I have a 2016 SQL Server freshly built - 13.0.5149.0 - OS 2016 (Microsoft Windows NT 6.3 (14393)). The environment is VMWare. No SQL Server HA configuration. It has a problem where CheckDB "stops" ...
4
votes
1answer
13k views

resource wait SQLCLR - wait_type CLR_SEMAPHORE by SPID 0

UPDATE In the comments under Aaron's post is an extensive explanation why I want to find this out, please read it if you want to know. The system is running some ETL, reporting services and a ...
4
votes
1answer
3k views

High Log Flush Wait Time and filling Transaction logs [closed]

I have problem with Log Flush Wait Time - as of now, they are averaging at 30000ms (min 0 max 35000); database itself is performing poorly, transaction logs are also growing beyond reasonable ...
4
votes
1answer
598 views

Why is there ASYNC_NETWORK_IO wait type on Shared Memory connections?

I have an app (windows service) local to the SQL Server box. It calls a stored procedure on the SQL Server box that returns a ton of data and thus causes ASYNC_NETWORK_IO wait. The database ...
4
votes
1answer
607 views

How to find out how much i/o resources a task, session, request or transaction is currently using?

How to find out how much i/o resources a task, session, request or transaction is currently using? by task I mean the DMV called DMV sys.dm_os_tasks. by session I mean the DMV sys.dm_exec_sessions ...
3
votes
2answers
9k views

CXPACKET SUSPENDED and NULL wait type

I was was running the query in this article: http://sqlity.net/en/708/why-cxpacket-waits-are-not-your-performance-problem/ To see what my threads were waiting on in regards to a suspended query with ...
3
votes
2answers
625 views

tsql Process running forever… what is it doing

Trying to create a big test DB, I have an SP that I created that uses a predefined list of tables (35 That I'm interested in) and multiplies the data in each one of them. In other words, A table ...
3
votes
1answer
2k views

async_network_io issues with BIDS

This is related to my previous question drastically different runtimes in BIDS and the SSRS Web Portal. I am struggling with refreshing some reports in BIDS because they run forever. I have now ...
3
votes
2answers
657 views

Wait types with queries

I have a query to find the wait types in which my system is suffering from. WITH [Waits] AS (SELECT [wait_type], [wait_time_ms] / 1000.0 AS [WaitS], ([wait_time_ms] - [...
3
votes
3answers
3k views

Collecting Wait Stats

We currently use a monitoring tool which shows us our top wait stats either by number of waiting tasks or total wait time. Below are the wait stats by number of tasks waiting and also wait time per ...
3
votes
2answers
11k views

Ideal values for wait time in SQL server

This is related to my own post here The SQL server starts everyday at 8:30 AM and stops around 9:30 PM.( So wait times will reset everyday) SQL server will be used by around 60 users simultaneously(...
3
votes
1answer
63 views

Nightly EDW Build Wait Stats

We are trying to determine our best MAXDOP and Cost Threshold settings for an EDW box. I setup a job to clear the wait stats before the build started and then capture the wait stats after the build ...
3
votes
1answer
1k views

What is the DPT_ENTRY_LOCK wait type?

We have a SQL Server 2016 Availability Group with 3 servers. Twice in the past 5 days we have had performance issues. 8a is our primary server, and 8b and 8c are the secondaries. We started having ...
3
votes
1answer
543 views

DIRTY_PAGE_POLL without activated Indirect Checkpoint

Since I encounter some performance issues on my SQL Server 2014 (12.0.2370.0 (X64)) I'm dealing with enormes amounts of different wait types. One of the top 5 wait type is "DIRTY_PAGE_POLL". I've ...
3
votes
1answer
2k views

WAIT STATS - high Wait Time on ASYNC_IO_COMPLETION

I currently look at my wait stats. I followed best practices explained by Paul Randal and go through the documents he references. Looking at the statistic slices I take once / day for a while now ...
3
votes
1answer
325 views

Excessive CPU use in vendor SQL Server DB

Background: I've got a SQL Server 2012 DB provided by a vendor so modification of queries and tables is limited. We do own the DB though, so we can add and maintain indexes. Indexes haven't been ...
3
votes
0answers
146 views

how does CXPACKETS relates to CXCONSUMER wait types?

when running a delete query to a table that has many foreign keys I get the following waits. I noticed that I have both CXPACKETS and CXCONSUMER wait types at the same time during of the execution ...
3
votes
0answers
282 views

PAGEIOLATCH_EX Wait on Target table of insert..select query

We are running SQL Server 2012 on Windows 2008 R2 with 256GB RAM and 90% memory allocated to SQL Server. No other Apps run on the server. I have a scenario where I’ve to copy a Source (staging) table ...
3
votes
0answers
215 views

PAGEIOLATCH_SH and WRITELOG waits

We have a slow overnight process which I was asked to look at with the top waits being PAGEIOLATCH_SH and WRITELOG I have been collecting information from sys.dm_io_virtual_file_stats and can see ...
3
votes
1answer
2k views

SQL Server performance issue (CXPACKET wait type)

I have a performance issue with production SQL Server 2012 which has 24 cores and 32 GB of RAM. From wait type I can see CXPACKET is on the top based on the following SQL Server metrics, should I ...
2
votes
1answer
1k views

Clarification on signal wait percent

I'm experiencing high Signal Wait percent while CPU utilisation is very low at one of our servers. I have gone through numerous articles online about Signal Waits and understand that it is the time ...