Random delays on opening connection to SQL Server - sql

In one of our systems we experience random delays when opening a connection to SQL Server.
The system is running Windows Server 2012 R2 Standard and SQL Server 2012, located on the same physical machine as our application.
Even when our application is idle, it is executing DB operations once every few seconds on average.
DB operations our application executes usually consist of 3 steps:
open a connection to SQL server
run a stored procedure
close the connection
Normally the first step takes a tiny fraction of second, while running a stored procedure may take much longer, depending on many factors.
The problem: opening a connection may randomly take 5-13 seconds. This only happens rarely, once in a few hours, even once in a day.
In other words this could happen once per a few thousand DB operations. We have not detected any discernable pattern in the timing of these delays.
There is nothing suspicious in the SQL Server log files.
Running SQL Server profiler does not seem practical, as the fault may not be exhibited for 10-20 hours.
We have not seen this phenomenon on any other machine.


It looks like we've fixed the problem. Somewhere I read a recommendation to try to use SQL Server authentication instead of Windows authentication. The problem discussed there was not exactly the same as ours but somewhat similar. Since connection string is used in every Open Connection operation, I decided to give it a try. As a result, our application has been working for 3 days in a row by now and there has not been a single incident of opening connection being slow. To put this in a context, before this fix we had several incidents in 24 hours on average, and not a single incident-free 24-hour period for the last two months.

Related

Web browsers slow down SQL server Express

Has anyone noticed the problem that SQL queries on SQL server 2019 Express take an abnormally long time if one of the web browsers is open on the Windows system? Specifically, I have a problem that a simple query takes 20 seconds or more. However, when I close the MS Edge browser, the query is done in less than a tenth of a second. E.g. I can also run a query, but nothing happens until I force Edge to close through Task Manager. The query then executes at the same moment Edge closes.
These symptoms are present on several different computers not just one.
Thanks!

What would cause SQL Server to stop writing to the error log?

Error logs for our SQL Server instance are gathering a large amount of data (250k records in a month) all day, then all of a sudden stop at roughly the same time of day (9:15pm), though on different days of the week and at seemingly random intervals of days.
This corresponds to other issues on the server: 1) jobs that move files to shares on the database server fail 2) I am not able to access the server via any method (tried RDP and SSMS). Once the servers are rebooted, SQL Server comes up and SQL Server error logging resumes.
Windows Event Viewer doesn't show any notable error messages for System (the other event logs have wrapped already).
The error logs are being written to the D:\ drive, which has over 100GB free currently. The error log files are in the range of tens of megabytes.
Appreciate any ideas on what might have caused this or how troubleshoot it. Thanks!

The cause appears to have been a corrupted maintenance plan. I discovered this by correlating the timing of the lock-up to the times the maintenance plan was running. The lack of logging made this difficult to confirm. Guessing that at least some parts of it ran normally, but got rolled back on restart.
The current fix was to disable the maintenance plan and replace it with a collection of jobs that do the same tasks. I will likely recreate the original maintenance plan if the server remains stable for another week or two. If we stay stable past that point, it should solidly confirm the maintenance plan as the source of the problem.

SQL server user session time out?

i use window application and i want to fire trigger after user session time out So ,
How to detect if user abort or his session timeout using SQ L server 2008 ?

SQL Server never times out sessions nor requests. A query issued against SQL Server may run for hours, days even, uninterrupted. You may be under the wrong impression that queries against SQL Server time out and get aborted because the ADO.Net client chooses to abort queries after 30 seconds, because that is the default value of the SqlCommand.CommandTimeout:
The time in seconds to wait for the
command to execute. The default is 30
seconds.
However, aborting the queries is a client specific behavior that SQL Server is not involved in. Other clients (eg. JDBC) use different policies.
Similarly, a SQL Server session never times out, even if not used for days. The application has to explicitly close the connection for its sessions to terminate. While is true that there are administrative ways to disconnect sessions (the KILL command) these are never to be used except for extreme last measure administrative operations.
So the good news is that you don't have to do anything, what you're asking for doesn't exists, or shouldn't be done to start with.

SQL Server taking a long time to return data to ColdFusion when using Flex

I am working on a Flex application that is connecting via Flash Remoting to ColdFusion 8 with a SQL Server 2005 database. Most of the time, everything runs fine. However, from time to time, it will take an exceptionally long time for SQL Server to return data from a stored procedure call to ColdFusion; returning data from CF to Flex is very fast. When this happens, I can run the exact same call from Management Studio on the SQL Server or a ColdFusion page on the CF server and get results immediately. The most recent occurrence of the issue took about 90 seconds to return data to CF. During the 90 second window, I was able to run the stored procedure in Management Studio several times.
I have tried using different drivers and this doesn't seem to matter. I have also kept an eye on server performance and haven't noticed anything unusual while this is happening. Has anyone seen this behavior before? Any ideas as to what I should be looking for.

While it's working slowly, can you run "sp_who2" against your SQL Server? If it's a blocking issue, you'll see rows that have a value in the "BlkBy" column, meaning that they'r waiting for another process to complete before they can continue.
If that's the case, then there's other troubleshooting to do so you can figure out what's causing the blocks. This article provides an overview of locking and troubleshooting blocks. If that's your issue, please update your question and add more details, and we can help you go from there!

Are you absolutely sure that the query being run in the sp is the same every time? For example, is it possible that when it slows down, the query has a different sort order? Possibly 9 times out of 10, the query returns quickly, and that 10th time is slow b/c the data you're getting is being sorted by some column that isn't indexed?
In these situations, I'd try to have a SQL Trace set up (using sql profiler) and let it run for a while. Once the situation happens, let it run through, and then analyze the trace. Confirm beyond doubt that the query being run is the same as other executions of the same sp

How to avoid Sql Query Timeout

I have RO access on a SQL View. This query below times out. How to avoid this?
select
count(distinct Status)
from
[MyTable] with (NOLOCK)
where
MemberType=6
The error message I get is:
Msg 121, Level 20, State 0, Line 0
A transport-level error has occurred when receiving results from the server (provider: TCP Provider, error: 0 - The semaphore timeout period has expired.)

Your query is probably fine. "The semaphore timeout period has expired" is a Network error, not a SQL Server timeout.
There is apparently some sort of network problem between you and the SQL Server.
edit: However, apparently the query runs for 15-20 min before giving the network error. That is a very long time, so perhaps the network error could be related to the long execution time. Optimization of the underlying View might help.
If [MyTable] in your example is a View, can you post the View Definition so that we can have a go at optimizing it?

Although there is clearly some kind of network instability or something interfering with your connection (15 minutes is possible that you could be crossing a NAT boundary or something in your network is dropping the session), I would think you want such a simple?) query to return well within any anticipated timeoue (like 1s).
I would talk to your DBA and get an index created on the underlying tables on MemberType, Status. If there isn't a single underlying table or these are more complex and created by the view or UDF, and you are running SQL Server 2005 or above, have him consider indexing the view (basically materializing the view in an indexed fashion).

You could put an index on MemberType.

Please check your Windows system event log for any errors specifically for the "Event Source: Dhcp". It's very likely a networking error related to DHCP. Address lease time expired or so. It shouldn't be a problem related to the SQL Server or the query itself.
Just search the internet for "The semaphore timeout period has expired" and you'll get plenty of suggestions what might be a solution for your problem. Unfortunately there doesn't seem to be the solution for this problem.

Do you have an index defined over the Status column and MemberType column?

how many records do you have? are there any indexes on the table? try this:
;with a as (
select distinct Status
from MyTable
where MemberType=6
)
select count(Status)
from a

My team were experiencing these issues intermittently with long running SSIS packages. This has been happening since Windows server patching.
Our SSIS and SQL servers are on separate VM servers.
Working with our Wintel Servers team we rebooted both servers and for the moment, the problem appears to have gone away.
The engineer has said that they're unsure if the issue is the patches or new VMTools that they updated at the same time. We'll monitor for now and if the timeout problems recur, they'll try rolling back the VMXNET3 driver, first, then if that doesn't work, take off the June Rollup patches.
So for us the issue is nothing to do with our SQL Queries (we're loading billions of new rows so it has to be long running).

This is happen because another instance of sql server is running. So you need to kill first then you can able to login to SQL Server.
For that go to Task Manager and Kill or End Task the SQL Server service then go to Services.msc and start the SQL Server service.

While I would be tempted to blame my issues - I'm getting the same error with my query, which is much, much bigger and involves a lot of loops - on the network, I think this is not the case.
Unfortunately it's not that simple. Query runs for 3+ hours before getting that error and apparently it crashes at the same time if it's just a query in SSMS and a job on SQL Server (did not look into details of that yet, so not sure if it's the same error; definitely same spot, though).
So just in case someone comes here with similar problem, this thread:
https://www.sqlservercentral.com/Forums/569962/The-semaphore-timeout-period-has-expired
suggest that it may equally well be a hardware issue or actual timeout.
My loops aren't even (they depend on sales level in given month) in terms of time required for each, so good month takes about 20 mins to calculate (query looks at 4 years).
That way it's entirely possible I need to optimise my query. I would even say it's likely, as some changes I did included new tables, which are heaps... So another round of indexing my data before tearing into VM config and hardware tests.
Being aware that this is old question: I'm on SQL Server 2012 SE, SSMS is 2018 Beta and VM the SQL Server runs on has exclusive use of 132GB of RAM (30% total), 8 cores, and 2TB of SSD SAN.