1. A system for providing improved application connectivity in a data source and clustered database environment, comprising: one or more computers including one or more processors, a clustered database, and a notification service associated with a plurality of database instances in the clustered database, wherein the notification service broadcasts notifications that describe state changes in the database instances of the clustered database; and an application server, having a database driver and data source and connection pools associated therewith, wherein the data source and connection pools are used by the application server to manage connections to the plurality of database instances in the clustered database, for use by applications at the application server, and wherein a connection is configured so that, during operation of an application using a web session that includes a query or update to the clustered database, the database driver records a state of information previously queried by the application from a database instance associated with the connection, so that, if the connection to the associated database instance fails, the database driver determines the state of information previously queried by the application, during the web session, from the database instance associated with the connection, and replays the web session against the clustered database to a point corresponding to the recorded state of information previously queried by the application, to process the query or update against the clustered database, so that the application does not itself receive an error or exception.