![]() ![]() ![]() The cache contains at most 10 MARS sessions. To minimize overhead and enhance performance, SqlClient caches the MARS session within a connection. When a connection is opened with MARS enabled, a logical session is created, which adds additional overhead. This implies that no other batches can execute within the same connection while a WAITFOR statement is waiting. If both statements are running under the same transaction, any changes made by a DML statement after the SELECT statement has started execution are not visible to the read operation.Ī WAITFOR statement inside a SELECT statement does not yield the transaction while it is waiting, that is, until the first row is produced. However, the DML statement must run to completion before the SELECT statement can make progress. If two batches are submitted under a MARS connection, one of them containing a SELECT statement, the other containing a DML statement, the DML can begin execution within execution of the SELECT statement. Parallel execution at the server is not a MARS feature. Any statements attempting to execute while an atomic batch is executing are blocked. However, data manipulation language (DML) and data definition language (DDL) statements execute atomically. Statement interleaving of SELECT and BULK INSERT statements is allowed. MARS operations execute synchronously on the server. However, if you wish to use MARS features in your applications, you should understand the following special considerations. In general, existing applications should not need modification to use a MARS-enabled connection. Dim connectionString As String = "Data Source=MSSQL1 " & _ #Active tables sql how to#The following connection string demonstrates how to disable MARS. "False" is the only valid value for disabling MARS. ![]() You can disable MARS by adding the "MultipleActiveResultSets=False" keyword pair to your connection string. "Initial Catalog=AdventureWorks Integrated Security=SSPI " + String connectionString = "Data Source=MSSQL1 " + "Initial Catalog=AdventureWorks Integrated Security=SSPI " & _ The following example demonstrates how to connect to an instance of SQL Server and how to specify that MARS should be enabled. "True" is the only valid value for enabling MARS. It can be enabled by adding the "MultipleActiveResultSets=True" keyword pair to your connection string. Modify the connection string as necessary for your environment. The connection strings provided assume that the database is installed on a server named MSSQL1. The following connection strings use the sample AdventureWorks database included with SQL Server. ![]()
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