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  • April 29, 2016

Testing WLS and ONS Configuration

Stephen Felts


Oracle Notification Service (ONS) is installed and configured as part of the
Oracle Clusterware installation. All nodes participating in the cluster are
automatically registered with the ONS during Oracle Clusterware installation. The
configuration file is located on each node in $ORACLE_HOME/opmn/conf/ons.config. See the Oracle documentation for further
information. This article focuses on the
client side.

Oracle RAC Fast Application Notification (FAN) events are available starting
in database 11.2. This is the minimum database
release required for WLS Active GridLink. FAN events are notifications sent by a cluster running Oracle RAC to
inform the subscribers about the configuration changes within the cluster. The supported FAN events are service up,
service down, node down, and load balancing advisories (LBA).

fanWatcher Program

You can optionally test your ONS configuration independent
of running WLS. This tests the
connection from the ONS client to the ONS server but not configuration of your
RAC services. See https://blogs.oracle.com/WebLogicServer/entry/fanwatcher_sample_program
for details to get, compile, and run the fanWatcher program. I’m assuming that you have WLS 10.3.6 or
later installed and you have your CLASSPATH set appropriately. You would run the test program using
something like

java fanWatcher
"nodes=rac1:6200,rac2:6200" database/event/service

If you are using the database client jar
files, you can handle more complex configurations with multiple clusters, for
example DataGuard, with something like

java fanWatcher "nodes.1=site1.rac1:6200,site1.rac2:6200

nodes.2=site2.rac1:6200,site2.rac2:6200" database/event/service

Note that a newline is used to separate multiple node
lists. You can also test with a wallet
file and password, if the ONS server is configured to use SSL communications.

Once this program is running, you should minimally
see occasional LBA notifications. If you
start or stop a service, you should see an associated event.

Auto ONS

It’s possible to run without specifying the ONS
information using a feature call auto-ONS.
The auto-ONS feature cannot be used
if you are running with

- an 11g driver or 11g database.
Auto-ONS depends on protocol flowing between the driver and the database server
and this feature was added in 12c.

- pre-WLS 12.1.3. Auto-ONS is supported starting in WLS 12.1.3.

- an Oracle wallet with SSL
communications. Configuration of the
wallet requires also configuring the ONS information.

- complicated ONS topology. In general, auto-ONS can figure out what you
need but there are cases where you need to specify it precisely. In WLS 12.2.1, an extension of the ONS
configuration allows for specifying the exact topology using a property node list. See http://docs.oracle.com/middleware/1221/wls/JDBCA/gridlink_datasources.htm#BABGJBIC
for more information.

If you have some configurations that
use an 11g driver or database and some that run with 12c driver/database, you
may want to just specify the ONS information all of the time instead of using
the auto-ONS simplification. The
fanWatcher link above indicates how to test fanWatcher using auto-ONS.

WLS ONS Configuration and Testing

The next step is to ensure that you have end-to-end
configuration running. That includes the
database service for which events will be generated to the AGL datasource that
processes the events for the corresponding service.

On the server side, the database service must be
configured RCLB enabled. RCLB is enabled for a service if the service GOAL (NOT
CLB_GOAL) is set to either SERVICE_TIME or THROUGHPUT. See the Oracle documentation for further
information on using srvctl to set this when creating the service.

On the WLS side, the key pieces are the URL and the
ONS configuration.

URL is configured using a long format with this service name specified. The URL can use
an Oracle Single Client
Access Name (SCAN) address, for example,


non-SCAN addresses with
LOAD_BALANCE=on, for example,


the URL is a complex topic - see the Oracle documentation for more information.

described above, the ONS configuration can be implicit using auto-ONS or
explicit. The trade-offs and
restrictions are also described above. The format of the explicit ONS information is described at http://docs.oracle.com/middleware/1221/wls/JDBCA/gridlink_datasources.htm#BABGJBIC.

you create the datasource using the administration console with explicit ONS
configuration, there is a button to click on to test the ONS configuration. This tests doing a simple handshake with the
ONS server.

course, the first real test of your ONS configuration with WLS is deploying the
datasource, either when starting the server or when targeting the datasource on
a running server.

In the administration console,
you can look at the AGL runtime monitoring page for ONS, especially if using
auto-ONS, to see the ONS configuration.

can look at the page for instances and check the affinity flag and instance
weight attributes that are updated on LBA events. If you stop a service using something like

stop service -db beadev -i beadev2 -s otrade

should also show up on this page with the weight and capacity going to 0.

you look at the server log (for example servers/myserver/logs/myserver.log) you
should see a message tracking the outage like the following.

<Info> <JDBC> … <Data
source JDBC Data Source-0 for service otrade received a service down event for
instance [beadev2].>

you want to see more information like the LBA events, you can enable the
JDBCRAC debugging using –Dweblogic.debug.DebugJDBCRAC=true. For example,

<JDBCRAC> ... lbaEventOccurred() event=service=otrade, database=beadev,
event=VERSION=1.0 database=beadev service=otrade { {instance=beadev1 percent=50
flag=GOOD aff=FALSE}{instance=beadev2 percent=50 flag=UNKNOWN aff=FALSE} }

will be a lot of debug output with this setting so it is not recommended for

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