The Oracle driver determines the timing of replay calls. Calls may be processed chronologically or using a lazy processing implementation depending on how the application changes the database state.
The replay is controlled by the Oracle 12c Database Server. For a replay to be approved, each replayed call must return exactly the same client visible state that was seen and potentially used by the application during the original call execution. The following section provides requirements and items to consider when using Application Continuity with WebLogic applications:. For this release, Application Continuity only supports read and write transactions.
XA transactions are not supported. See Selecting the Driver for Application Continuity. Deprecated oracle. Occurrences should be changed to use either the corresponding oracle. Oracle recommends using the standard java. Application Continuity works by storing intermediate results in memory. An application may run slower and require significantly more memory than running without the feature.
Using the WebLogic statement cache is not supported. The size of the WebLogic statement cache must be set to 0. There are additional limitations and exceptions to the Application Continuity feature which may affect whether your application can use Replay.
For example:. The following sections provide information on how to implement Application Continuity in your environment:. The administration console does not have an entry for a replay driver. To configure the JDBC replay data source, you must manually replace the existing Oracle data source class with the replay data source class oracle. Make sure the Database Type is Oracle. See Requirements and Considerations.
To create a connection initialization callback, your application must implement the initialize java. Connection connection method of the oracle. ConnectionInitializationCallback interface. Only one callback can be created per connection pool. The callback is ignored if a labeling callback is registered for the connection pool. Otherwise, the callback is executed at every connection check out from the pool and at each successful reconnect following a recoverable error at replay.
Use of the same callback at run time and at replay ensures that exactly the same initialization that was used when the original session was established is used during the replay. If the callback invocation fails, replay is disabled on that connection. Only one callback may be registered on a connection pool. The following example demonstrates registering an initialization callback that is implemented in the MyConnectionInitializationCallback class:.
On the client-side, drivers can be used in Java applications or Java applets that run either on the client or in the middle tier of a three-tier configuration. On the server-side, this driver is used to access a remote Oracle Database instance or another session on the same database. Transaction Guard feature provides a generic infrastructure for at-most-once execution during planned and unplanned outages and duplicate submissions.
Transaction Guard feature along with Application Continuity feature provides transparent session recovery and replay of SQL statements queries and DMLs since the beginning of the in-flight transaction. Application Continuity provides a general purpose, application-independent infrastructure that enables recovery of work from an application perspective, after the occurrence of a planned or unplanned outage. It provides the following benefits:.
This driver can be downloaded along with the Java applet that is being run in a browser. The HTTP protocol, which is usually used for communication over a network, is stateless. After the JDBC Thin driver establishes the database connection, the communication between the browser and the database is stateful and in a two-tier configuration. This section describes what you must do to connect an applet to a database.
This description includes how to use the Connection Manager feature of Oracle Database, or signed applets if you are connecting to a database that is running on a different host from the Web server. It also describes how your applet can connect to a database through a firewall. The section concludes with how to package and deploy the applet.
The most common task of an applet using the JDBC driver is to connect to and query a database. This is the host on which the Web server is running.
This means that without these steps, your applet can connect only to a database that is running on the same host as the Web server. If your database and Web server are running on the same host, then there is no issue and no special steps are required.
You can connect to the database as you would from an application. As with connecting from an application, there are two ways in which you can specify the connection information to the driver. For example, if the database to which you want to connect resides on the localost , at port , and service name orcl , and you want to connect with user name HR and password hr , then use either of the two following connection strings:. However, a Web server and database server both require many resources.
You seldom find both servers running on the same computer. Usually, your applet connects to a database on a host other than the one on which the Web server runs. If you want your applet to connect to a database running on a different computer, then you have the following options:. Use the Oracle Connection Manager on the host computer. The applet can connect to the Connection Manager, which connects to a database on another computer. Use signed applets, which can request socket connection privileges to other computers.
Your applet can also take advantage of the data encryption and integrity checksum features of the Advanced Security option of Oracle Database. If you are connecting to a database on a host other than the one on which the Web server is running, then you must overcome applet security restrictions. You can do this in the following ways:. The Oracle Connection Manager is a lightweight, highly scalable program that can receive Oracle Net packets and retransmit them to a different server.
To a client running Oracle Net, the Connection Manager looks exactly like a database server. Figure illustrates the relationship between the applet, the Oracle Connection Manager, and the database. Installing and Running the Oracle Connection Manager. You must install the Connection Manager, available on the Oracle distribution media, onto the Web server host.
The options you can declare in a CMAN. ORA file include firewall and connection pooling support. Here is an example of a very simple CMAN. ORA file. Replace web-server-host with the name of your Web server host. The fourth line in the file indicates that the Connection Manager is listening on port Each database can have multiple connection and authentication methods. Switch to a different method from the dropdown menu. You can use the first tab to connect, and then see the created URL in the second tab.
Connectivity Troubleshooting If you get problems connecting to the database, please remember : Press the ping button in the connection dialog to make sure the host and port are reachable. Enable Remote connections as they are not always enabled by default.
This may require configuration changes. Windows Firewall may block the communication.
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