C# – SQL Server long running query randomly timeout through .Net

cnetsql serversqlclienttimeout

We have a program that connects to our DB and run some Stored Procedures to get some data.

The database is a SQL Server 2008 and the program runs locally. The connection is via TCP/IP, but shared memory is enabled. And the timeout of the connection string is set to 45 sec.

When we run them through SQL Server Management Studio, it takes 0-5 seconds to run.
When we run it through code, it randomly times out.

To make some test, we increased the timeout from 45sec to few minutes. And also to discard any blocking issue we checked that the Stored Procedures only "selects" data (with no insert or update statement). And we have tried several table modifiers for the select statements like: nolock, readpast, …

Also I checked sp_who2 and dbcc opentran() and nothing is blocked… and the SPID of the .Net is running command .... For more details while the .Net is waiting a DB answer, through SQL Server Management Studio I can run the same statement (Stored Procedure or Select) without problems.

Any suggestion of what is happening?

Best Answer

The connection string timeout only influences the login timeout. You seems to hit a command timeout, and that can be changed only by modifying the CommandTimeout. The default value is 30 seconds, the recommended value is 0 (infinite timeout).

As for why your procedure hits random slow execution, I recommend to start by reading Slow in the Application, Fast in SSMS? Understanding Performance Mysteries

BTW, your query is likely not blocked. It executes a different plan that simply takes that long to execute. Checking for last_wait_type in sys.dm_exec_requests will likely reveal IO waits (PAGEIOLATCH, after to chasse any red-herring CXPACKET down the sys.dm_os_workers join...). But there is no point repeating the far more comprehensive and excellent article by Erland Sommarskog I originally linked.

Syntax:

ALTER TABLE {TABLENAME} 
ADD {COLUMNNAME} {TYPE} {NULL|NOT NULL} 
CONSTRAINT {CONSTRAINT_NAME} DEFAULT {DEFAULT_VALUE}
WITH VALUES

Example:

ALTER TABLE SomeTable
        ADD SomeCol Bit NULL --Or NOT NULL.
 CONSTRAINT D_SomeTable_SomeCol --When Omitted a Default-Constraint Name is autogenerated.
    DEFAULT (0)--Optional Default-Constraint.
WITH VALUES --Add if Column is Nullable and you want the Default Value for Existing Records.

Notes:

Optional Constraint Name:
If you leave out CONSTRAINT D_SomeTable_SomeCol then SQL Server will autogenerate
a Default-Contraint with a funny Name like: DF__SomeTa__SomeC__4FB7FEF6

Optional With-Values Statement:
The WITH VALUES is only needed when your Column is Nullable
and you want the Default Value used for Existing Records.
If your Column is NOT NULL, then it will automatically use the Default Value
for all Existing Records, whether you specify WITH VALUES or not.

How Inserts work with a Default-Constraint:
If you insert a Record into SomeTable and do not Specify SomeCol's value, then it will Default to 0.
If you insert a Record and Specify SomeCol's value as NULL (and your column allows nulls),
then the Default-Constraint will not be used and NULL will be inserted as the Value.

Notes were based on everyone's great feedback below.
Special Thanks to:
@Yatrix, @WalterStabosz, @YahooSerious, and @StackMan for their Comments.

Sql – How to return only the Date from a SQL Server DateTime datatype

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, @your_date))

for example

SELECT DATEADD(dd, 0, DATEDIFF(dd, 0, GETDATE()))

gives me

2008-09-22 00:00:00.000

Pros:

No varchar<->datetime conversions required
No need to think about locale

Best Answer

Related Solutions

Sql – Add a column with a default value to an existing table in SQL Server

Syntax:

Example:

Notes:

Sql – How to return only the Date from a SQL Server DateTime datatype

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