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The common parameters of the connection string in C # describe the Provider setting or return the name of the connection program provided. It is only used for the OLeDbConnection object Connection Timeout to wait for the connection time (in seconds) to connect to the server before terminating the attempt and generating an exception. The default value is the database name of the 15-second Initial Catalog or Database connection Data Source or the SQL Server service signature used when the Server connection is opened, or the Access database file name (localhost or 127.0.0.1) Password or pwdSql Server login password User ID or uidSql Server login account Integrated Sercuity determines whether the connection is a secure connection. Possible values are True,False and SSPI (SSPI and True are synonymous)

The above parameters are case-insensitive. For example, uid,UID,Uid represents the connected database user.

When the Integrated Security parameter is used for local windows authentication login, its value should be set to True, for example ("server=localhost;database=mydb;Integrated security=true")

II. Net database connection pool timeout problem (1) what is the database Connection Pool connection pool

Whenever the program needs to read and write the database. Connection.Open () uses ConnectionString to connect to the database, which establishes a connection for the program and keeps it open, after which the program can query / update the database using the T-SQL statement. When executed to Connection.Close (), the database closes the current connection.

But if my program needs to open and close connections from time to time (such as ASP.Net or Web Service), for example, when Http Request is sent to the server, we need to open Connection and use Select* from Table to return a DataTable/DataSet to the client / browser, and then close the current Connection. There is no doubt that it is a waste for the whole system to operate Open/Close Connection so frequently every time.

ADO.Net Team gives a better solution. Save the previous Connection and give the previous Connection to the next connection the next time you need to open the connection. This is Connection Pool.

(2) the operation mode of database Connection Pool connection pool

1. When a program executes Connection.open (), ADO.net needs to determine whether the connection supports Connection Pool (Pooling defaults to True).

(1) if False is specified, ADO.net creates a connection with the database and returns it to the program.

(2) if specified as True,ADO.net, a Connection Pool is created based on the ConnectString, and then the Connection Pool is populated with Connection. The number of Connection populated is determined by the Min Pool Size (default is 0) attribute. For example, if you specify 5, ADO.net opens five connections to the SQL database at a time, then saves four Connection in Connection Pool and returns one Connection to the program.

2. When the program is executed to Connection.close (). If Pooling is True,ADO.net, put the current Connection into Connection Pool and maintain a connection to the database.

At the same time, the Connection Lifetime (default is 0) attribute is also judged. 0 means infinity. If the Connection exists longer than the Connection LifeTime,ADO.net, the Connection that will be closed will be disconnected from the database instead of being re-saved to the Connection Pool.

3. When the current Connection.Open () is executed, ADO.Net will determine whether the new ConnectionString is consistent with the connectionString of the Connection previously stored in Connection Pool.

4. ADO.net needs to determine whether there is a Connection that can be used in the current Connection Pool (not occupied by other programs). If not, ADO.net needs to determine the Max Pool Size set by ConnectionString (default is 100).

(1) if all the Connection in the Connection Pool does not reach the Max Pool Size,ADO.net, it will connect to the database again, create a connection, and then return the Connection to the program.

(2) if the MaxPoolSize,ADO.net has been reached, no new connections will be created again, but wait for the Connection occupied by other programs in the Connection Pool to be released. This waiting time is limited by SqlConnection.ConnectionTimeout (default is 15 seconds), that is, if the time exceeds 15 seconds, SqlConnection will throw a timeout error.

5. If a Connection is available, the Connection extracted from the Connection Pool is not directly returned to the program. ADO.net also needs to check whether the ConnectionReset attribute of the ConnectionString (default is True) needs to reset the Connection for the last time.

(3) the configuration of max pool size by ASP.NET program

Add the following to the connection string:

Pooling=true;min pool size=5;max pool size=512

Where Max Pool Size defaults to 100 if not set, and the theoretical maximum is 32767. The maximum number of connections is the maximum number of connections that can be requested by the connection pool. if the database connection request exceeds this number, the subsequent database connection request will be added to the waiting queue, which will affect the subsequent database operation. In the wait queue, the default time to wait for a connection to the server is 15 seconds.

The default connection pool size is generally 100.

(4) check the number of select * from sysprocesses where dbid= db_id occupied by the application pool ('database name')

Several pieces of data from the query prove that there are several connections.

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