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Oracle® Database JDBC Developer's Guide,
11g Release 2 (11.2)

Part Number E16548-02
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B Oracle RAC Fast Application Notification

Oracle Database 11g Release 2 (11.2) introduces a new set of APIs for Oracle RAC Fast Application Notification (FAN) events. These APIs provide an alternative for taking advantage of the high-availability (HA) features of Oracle Database, if you do not use Universal Connection Pool or Oracle JDBC connection caching. These APIs are not a part of Oracle JDBC APIs.

This appendix covers the following topics:

This feature depends on the Oracle Notification System (ONS) message transport mechanism. This feature requires configuring your system, servers, and clients to use ONS.

For using Oracle RAC Fast Application Notification, the simplefan.jar file must be present in the classpath, and either the ons.jar file must be present in the classpath or an Oracle Notification Services (ONS) client must be installed and running in the client system.

Overview of Oracle RAC Fast Application Notification

The Oracle RAC Fast Application Notification (FAN) feature provides a simplified API for accessing FAN events through a callback mechanism. This mechanism enables application code to receive a callback when a FAN event occurs. These APIs are referred to as Oracle RAC FAN APIs in this appendix.

The Oracle RAC FAN APIs provide FAN event notification for developing more responsive applications that can take full advantage of Oracle Database HA features. If you do not want to use Universal Connection Pool, but want to work with FAN events implementing your own connection cache, then you should use Oracle RAC Fast Application Notification.

Note:

  • If you do not want to implement your own connection cache, then you should use Universal Connection Pooling to get all the advantages of Oracle RAC Fast Application Notification, along with many additional benefits. For more information on Universal Connection Pooling, refer to Oracle Universal Connection Pool for JDBC Developer's Guide.

  • Starting from Oracle Database 11g Release 2 (11.2), implicit connection cache has been deprecated, and replaced with Universal Connection Pool (UCP) for JDBC. Oracle recommends that you take advantage of the new architecture, which is more powerful and offers better performance. Refer to the following link for more information

    http://www.oracle.com/technology/tech/java/sqlj_jdbc/index.html
    

The Oracle RAC FAN APIs enable application code to receive and respond to FAN event notifications sent by Oracle RAC. This is achieved by enabling the code to respond to FAN events in the following way:

This feature exposes a subset of FAN events, which are the notifications sent by a cluster running Oracle RAC, to inform the subscribers about the configuration changes within the cluster. The supported FAN events are the following:

Note:

If you want to implement your own connection cache, only then you should use Oracle RAC Fast Application Notification. Otherwise, you should use Universal Connection Pooling to get all the advantages of Oracle RAC Fast Application Notification, along with many additional benefits. For more information on Universal Connection Pooling, refer to Oracle Universal Connection Pool for JDBC Developer's Guide.

Installing and Configuring Oracle RAC Fast Application Notification

You can install the Oracle RAC FAN APIs by performing the following steps:

  1. Download the simplefan.jar file from the following link

    http://www.oracle.com/technology/tech/java/sqlj_jdbc/index.html
    
  2. Add the simplefan.jar file to the classpath.

  3. Perform the following in your Java code:

    1. Get an instance of the FanManager class by using the getInstance method.

    2. Configure the event daemon using the configure method of the FanManager class. The configure method sets the following properties:

      onsNodes: A comma separated list of host:port pairs of ONS daemons that the ONS runtime in this Java VM should communicate with. The host in a host:port pair is the host name of a system running the ONS daemon. The port is the local port configuration parameter for that daemon.

      onsWalletFile: The path name of the ONS wallet file. The wallet file is the path to a local wallet file used by SSL to store SSL certificates. Same as wallet file configuration parameter to ONS daemon.

      onsWalletPassword: The password for accessing the ONS wallet file.

For a detailed description of the Oracle RAC FAN APIs, refer to Oracle Database RAC FAN Events Java API Reference.

Configuration of ONS

The Java API for Oracle RAC FAN Events depends on the Oracle Notification System (ONS) service. This section describes how to configure ONS. It covers the following topics:

Overview of ONS Configuration File

ONS configuration is controlled by the ONS configuration file, ORACLE_HOME/opmn/conf/ons.config. This file tells the ONS daemon how it should behave. Configuration information within ons.config is defined in simple name and value pairs.

Some parameters in the ons.config file are required and some are optional. Table B-1 lists the required ONS configuration parameters and Table B-2 lists the optional ONS configuration parameters.

Table B-1 Required ONS Configuration Parameters

Parameter Explanation

localport

The port that ONS binds to on the local host interface to talk to local clients.

For example, localport=4100

remoteport

The port that ONS binds to on all interfaces for talking to other ONS daemons.

For example, remoteport=4200

nodes

A list of other ONS daemons to talk to. Node values are given as a comma-delimited list of either host names or IP addresses plus ports. The port value that is given is the remote port that each ONS instance is listening on. In order to maintain an identical file on all nodes, the host:port of the current ONS node can also be listed in the nodes list. It will be ignored when reading the list.

For example, nodes=myhost.example.com:4200,123.123.123.123:4200

The nodes listed in the nodes line correspond to the individual nodes in the Oracle RAC instance. Listing the nodes ensures that the middle-tier node can communicate with the Oracle RAC nodes. At least one middle-tier node and one node in the Oracle RAC instance must be configured to see one another. As long as one node on each side is aware of the other, all nodes are visible. You need not list every single cluster and middle-tier node in the ONS configuration file of each Oracle RAC node. In particular, if one ONS configuration file cluster node is aware of the middle tier, then all nodes in the cluster are aware of it.


Table B-2 Optional ONS Configuration Parameters

Parameter Description

loglevel

The level of messages that should be logged by ONS. This value is an integer that ranges from 1, which indicates least messages logged, to 9, which indicates most messages logged. The default value is 3.

For example, loglevel=3

logfile

A log file that ONS should use for logging messages. The default value for log file is $ORACLE_HOME/opmn/logs/ons.log.

For example, logfile=/private/oraclehome/opmn/logs/myons.log

walletfile

The wallet file used by the Oracle Secure Sockets Layer (SSL) to store SSL certificates. If a wallet file is specified to ONS, then it uses SSL when communicating with other ONS instances and require SSL certificate authentication from all ONS instances that try to connect to it. This means that if you want to turn on SSL for one ONS instance, then you must turn it on for all instances that are connected. This value should point to the directory where your ewallet.p12 file is located.

For example, walletfile=/private/oraclehome/opmn/conf/ssl.wlt/default

useocr

The value, reserved for use on the server-side, to indicate ONS whether it should store all Oracle RAC nodes and port numbers in Oracle Cluster Registry (OCR) instead of the ONS configuration file or not. A value of useocr=on is used to store all Oracle RAC nodes and port numbers in Oracle Cluster Registry (OCR).

Do not use this option on the client-side.


The ons.config file allows blank lines and comments on lines that begin with the number sign (#).

Configuring Client-Side ONS

You can access the client-side ONS through ORACLE_HOME/opmn. On the client-side, there are two ways to set up ONS:

Example B-1 illustrates how a sample configuration file may look.

Example B-1 Example of a Sample ons.config File

# This is an example ons.config file
#
# The first three values are required
localport=4100
remoteport=4200
nodes=racnode1.example.com:4200,racnode2.example.com:4200

After configuring ONS, you start the ONS daemon with the onsctl command. It is the user's responsibility to make sure that an ONS daemon is running at all times.

Using the onsctl Command

After configuring, use ORACLE_HOME/opmn/bin/onsctl to start, stop, reconfigure, and monitor the ONS daemon. Table B-3 is a summary of the commands that onsctl supports.

Table B-3 onsctl Commands

Command Effect Output

start

Starts the ONS daemon

onsctl: ons started

stop

Stops the ONS daemon

onsctl: shutting down ons daemon...

ping

Verifies whether or not the ONS daemon is running

ons is running ...

reconfig

Triggers a reload of the ONS configuration without shutting down the ONS daemon

 

help

Prints a help summary message for onsctl

 

detailed

Prints a detailed help message for onsctl

 

Using Oracle RAC Fast Application Notification

Example B-2 provides an example to use Oracle RAC Fast Application Notification in your code. This example code prints the event data to the standard output device.

This example code demonstrates sample usages of Oracle RAC FAN APIs by overloading the handleFanEvent method to accept different FAN event notifications as arguments. The example code also displays event data such as

Example B-2 Example of Sample Code Using Oracle RAC FAN API

...
...Properties props = new Properties();
props.putProperty(“serviceName”, “gl”);
FanSubscription sub = FanManager.getInstance().subscribe(props);
sub.addListener(new FanEventListener()) {
  public void handleFanEvent(ServiceDownEvent event) {
    try {
      System.out.println(event.getTimestamp());
      System.out.println(event.getServiceName());
      System.out.println(event.getDatabaseUniqueName());
      System.out.println(event.getReason());
      ServiceMemberEvent me = se.getServiceMemberEvent();
      if (me != null) {
        System.out.println(me.getInstanceName());
        System.out.println(me.getNodeName());
        System.out.println(me.getServiceMemberStatus());
      }
      ServiceCompositeEvent ce = se.getServiceCompositeEvent();
      if (ce != null) {
        System.out.println(ce.getServiceCompositeStatus());
      }
    }
    catch (Throwable t) {
      // handle all exceptions and errors
      t.printStackTrace(System.err);
    }
  }
  public void handleFanEvent(NodeDownEvent event) {
    try {
      System.out.println(event.getTimestamp());
      System.out.println(ne.getNodeName());
      System.out.println(ne.getIncarnation());
    }
    catch (Throwable t) {
      // handle all exceptions and errors
      t.printStackTrace(System.err);
    }
  }
  public void handleFanEvent(LoadAdvisoryEvent event) {
    try {
      System.out.println(event.getTimestamp());
      System.out.println(le.getServiceName());
      System.out.println(le.getDatabaseUniqueName());
      System.out.println(le.getInstanceName());
      System.out.println(le.getPercent());
      System.out.println(le.getServiceQuality());
      System.out.println(le.getLoadStatus());
    }
    catch (Throwable t) {
      // handle all exceptions and errors
      t.printStackTrace(System.err);
    }
  }
});

Implementing a Connection Cache

You must implement your own connection cache for using Oracle RAC FAN APIs. Consider the following points before you implement a connection cache using the Oracle RAC FAN APIs: