дополню Valery Shiskin
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpconConnectionPoolingForSQLServerNETDataProvider.asp
NameDefaultDescription Connection Lifetime 0 When a connection is returned to the pool, its creation time is compared with the current time, and the connection is destroyed if that time span (in seconds) exceeds the value specified by Connection Lifetime. This is useful in clustered configurations to force load balancing between a running server and a server just brought online. A value of zero (0) will cause pooled connections to have the maximum time-out. Connection Reset 'true' Determines whether the database connection is reset when being removed from the pool. For Microsoft SQL Server version 7.0, setting to false avoids making an additional server round trip when obtaining a connection, but you must be aware that the connection state, such as database context, is not being reset. Enlist 'true' When true, the pooler automatically enlists the connection in the current transaction context of the creation thread if a transaction context exists. Max Pool Size 100 The maximum number of connections allowed in the pool. Min Pool Size 0 The minimum number of connections maintained in the pool. Pooling 'true' When true, the connection is drawn from the appropriate pool, or if necessary, created and added to the appropriate pool.
+ http://msdn.microsoft.com/library/default.asp?url=/library/en-us/dnsqlmag03/html/The_NETConnectionPoolLifeguard.asp