C# – any limit of SQL Server connection count

ado.netcnetsql serversql-server-2008

I am using SQL Server 2008 Enterprise + C# + ADO.Net + .Net 3.5. I am using sp_who2 or sys.dm_exec_connections to find active connections numbers (let me know if my method to find active connection numbers are wrong). For some heavy database consumer application, I can find even active connection count > 1000.

I am wondering whether there are any upper bound limitations of active connection numbers of SQL Server?

thanks in advance,
George

Best Answer

It is a per-instance, not per database, configuration. You can check the current value in sys.configurations and change it with sp_configure. The relevant option is user connections:

Use the user connections option to specify the maximum number of simultaneous user connections allowed on Microsoft SQL Server. The actual number of user connections allowed also depends on the version of SQL Server you are using and the limits of your application or applications and hardware. SQL Server allows a maximum of 32,767 user connections.

1000 of connections is not an exceedingly high number. On high end systems the server can listen on multiple ports affinitized to NUMA nodes and have hundreds and thousands of clients connected to each node.

Note that the number of connections is different from the number of requests, ie. connections actively executing something, sys.dm_exec_requests. Each Request requires one or more workers and the number of workers is configured with the max worker threads option.

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

Related Topic