19 Working with Oracle Messaging Gateway

Creating a Messaging Gateway Agent

You can use DBMS_MGWADM.CREATE_AGENT to create additional Messaging Gateway agents. The Messaging Gateway default agent, DEFAULT_AGENT, is automatically created when Messaging Gateway is installed and will always exist.

Agents can be configured with an agent user, connection information, database service, and resource limits when the agent is created, or at a later time using DBMS_MGWADM.ALTER_AGENT. A Messaging Gateway agent must be configured with a database user that has been granted the role MGW_AGENT_ROLE before the agent can be started.

Example 19-1 creates the agent named myagent and specifies the database connection information for the agent user. Default values are used for all other parameters.

SQL> exec DBMS_MGWADM.CREATE_AGENT(
                         agent_name  => 'myagent',
                         username    => 'mgwagent',
                         password    => 'mgwagent_password',
                         database    => 'mydatabase');

Removing a Messaging Gateway Agent

A Messaging Gateway agent can be removed by calling DBMS_MGWADM.REMOVE_AGENT. Before an agent can be removed, all Messaging Gateway links associated with the agent must be removed and the agent shut down. The default agent, DEFAULT_AGENT, cannot be removed. Example 19-2 removes the agent named myagent.

SQL> exec DBMS_MGWADM.REMOVE_AGENT(agent_name   => 'myagent');

Database Connection

The Messaging Gateway agent runs as a process external to the database. To access Oracle Database Advanced Queuing and the Messaging Gateway packages, the Messaging Gateway agent needs to establish connections to the database. You can use DBMS_MGWADM.ALTER_AGENT to set the user name, password and the database connect string that the Messaging Gateway agent will use for creating database connections. The user must be granted the role MGW_AGENT_ROLE before the Messaging Gateway agent can be started.

Example 19-3 shows the Messaging Gateway default agent being configured for user mgwagent with password mgwagent_password using net service name mydatabase.

SQL> exec DBMS_MGWADM.ALTER_AGENT (
                             agent_name => 'default_agent',
                             username   => 'mgwagent', 
                             password   => 'mgwagent_password',
                             database   => 'mydatabase');

Resource Limits

You can use DBMS_MGWADM.ALTER_AGENT to set resource limits for the Messaging Gateway agent. For example, you can set the heap size of the Messaging Gateway agent process and the number of propagation threads used by the agent process. The default values are 64 MB of memory heap and one propagation thread. For named agents, these values can also be specified when the agent is created by DBMS_MGWADM.CREATE_AGENT.

Example 19-4 sets the heap size to 96 MB and two propagation threads for the agent myagent.

SQL> exec DBMS_MGWADM.ALTER_AGENT(
                        agent_name  => 'myagent',
                        max_memory  => 96,
                        max_threads => 2);

The memory heap size and the number of propagation threads cannot be altered when the Messaging Gateway agent is running.

Starting the Oracle Messaging Gateway Agent

After the Messaging Gateway agent is configured, you can start the agent with DBMS_MGWADM.STARTUP. Example 19-5 shows how to start the default agent and agent myagent.

SQL> exec DBMS_MGWADM.STARTUP;
SQL> exec DBMS_MGWADM.STARTUP ('myagent');

You can use the MGW_GATEWAY view to check the status of the Messaging Gateway agent, as described in Chapter 21, "Monitoring Oracle Messaging Gateway".

Shutting Down the Oracle Messaging Gateway Agent

You can use DBMS_MGWADM.SHUTDOWN to shut down the Messaging Gateway agent. Example 19-6 shows how to shut down the Messaging Gateway default agent and agent myagent.

SQL> exec DBMS_MGWADM.SHUTDOWN;
SQL> exec DBMS_MGWADM.SHUTDOWN ('myagent');

You can use the MGW_GATEWAY view to check if the Messaging Gateway agent has shut down successfully, as described in Chapter 21, "Monitoring Oracle Messaging Gateway".

Oracle Messaging Gateway Agent Scheduler Job

Messaging Gateway uses a Scheduler job to start the Messaging Gateway agent. This job is created when procedure DBMS_MGWADM.STARTUP is called. When the job is run, it calls an external procedure that creates the Messaging Gateway agent in an external process. The job is removed after:

• The agent shuts down because DBMS_MGWADM.SHUTDOWN was called

• The agent terminates because a non-restartable error occurs

Messaging Gateway uses DBMS_SCHEDULER to create a repeatable Scheduler job with a repeat interval of one minute. The job is owned by SYS. A repeatable job enables the Messaging Gateway agent to restart automatically when a given job instance ends because of a database shutdown, database malfunction, or a restartable error. Only one instance of a Messaging Gateway agent job runs at a given time.

Each agent uses a Scheduler job class to specify the service affinity for the agent's Scheduler job. The job class will be configured with the database service specified by DBMS_MGWADM.CREATE_AGENT or DBMS_MGWADM.ALTER_AGENT. A database administrator is responsible for setting up the database service. If no database service is specified, the default database service that maps to every instance is used.

The name of the Scheduler job class used by the Messaging Gateway default agent is SYS.MGW_JOBCLS_DEFAULT_AGENT. The Scheduler job used by the default agent is SYS.MGW_JOB_DEFAULT_AGENT.

The name of the Scheduler job class used by a Messaging Gateway named agent is SYS.MGW_JOBCLS_<agent_name>. The Scheduler job used by a named agent is SYS.MGW_JOB_<agent_name>.

If the agent job encounters an error, then the error is classified as either a restartable error or non-restartable error. A restartable error indicates a problem that might go away if the agent job were to be restarted. A non-restartable error indicates a problem that is likely to persist and be encountered again if the agent job restarts. ORA-01089 (immediate shutdown in progress) and ORA-28576 (lost RPC connection to external procedure) are examples of restartable errors. ORA-06520 (error loading external library) is an example of a non-restartable error.

Messaging Gateway uses a database shutdown trigger. If the Messaging Gateway agent is running on the instance being shut down, then the trigger notifies the agent of the shutdown, and upon receipt of the notification, the agent will terminate the current run. The job scheduler will automatically schedule the job to run again at a future time.

If a Messaging Gateway agent job instance ends because of a database malfunction or a restartable error detected by the agent job, then the job will not be removed and the job scheduler will automatically schedule the job to run again at a future time.

The MGW_GATEWAY view shows the agent status, database service, and the database instance on which the Messaging Gateway agent is current running. The Oracle Scheduler views provide information about Scheduler jobs, job classes, and job run details.

Running the Oracle Messaging Gateway Agent on Oracle RAC

While the Messaging Gateway job startup and shutdown principles are the same for Oracle Real Application Clusters (Oracle RAC) and non-Oracle RAC environments, there are some things to keep in mind for an Oracle RAC environment.

A single process of each configured Messaging Gateway agent can be running, even in an Oracle RAC environment. For example, if the default agent and two named agents have been configured with an agent user, then one instance of all three agents could be running at the same time. The database service associated with each agent determines the service affinity of the agent's Scheduler job, and thus, the database instance on which the agent process can run.

When a database instance is shut down in an Oracle RAC environment, the Messaging Gateway shutdown trigger will notify the agent to shut down only if the Messaging Gateway agent is running on the instance being shut down. The job scheduler will automatically schedule the job to be run again at a future time, either on another instance, or if the job can only run on the instance being shut down, when that instance is restarted.

Oracle recommends that all database connections made by the Messaging Gateway agent be made to the instance on which the Messaging Gateway agent process is running. This ensures correct failover behavior in an Oracle RAC environment.

If a Messaging Gateway agent has been associated with a database service, the agent's Scheduler job will not run unless that service is current enabled on a running instance. When you shut down a database Oracle stops all services to that database and you may need to manually restart the services when you start the database.

Creating a WebSphere MQ Base Java Link

A WebSphere MQ Base Java link is created by calling DBMS_MGWADM.CREATE_MSGSYSTEM_LINK with the following information provided:

• Interface type: DBMS_MGWADM.MQSERIES_BASE_JAVA_INTERFACE

• WebSphere MQ connection information:

  • Host name and port number of the WebSphere MQ server

  • Queue manager name

  • Channel name

  • User name and password

• Maximum number of messaging connections allowed

• Log queue names for inbound and outbound propagation

• Optional information such as:

  • Send, receive, and security exits

  • Character sets

Example 19-7 configures a WebSphere MQ Base Java link mqlink. The link is configured to use the WebSphere MQ queue manager my.queue.manager on host myhost.mydomain and port 1414, using WebSphere MQ channel mychannel.

This example also sets the option to register a WebSphere MQ SendExit class. The class mySendExit must be in the CLASSPATH set in mgw.ora. The Messaging Gateway default agent (DEFAULT_AGENT) is responsible for the link and all propagation jobs using the link.

DECLARE
  v_options sys.mgw_properties;
  v_prop sys.mgw_mqseries_properties;
BEGIN
  v_prop := sys.mgw_mqseries_properties.construct();
  
  v_prop.interface_type := dbms_mgwadm.MQSERIES_BASE_JAVA_INTERFACE;
  v_prop.max_connections := 1;
  v_prop.username := 'mqm';
  v_prop.password := 'mqm';
  v_prop.hostname := 'myhost.mydomain';
  v_prop.port     := 1414;
  v_prop.channel  := 'mychannel';
  v_prop.queue_manager := 'my.queue.manager';
  v_prop.outbound_log_queue := 'mylogq';
  
  -- Specify a WebSphere MQ send exit class 'mySendExit' to be associated with
  -- the queue. 
  -- Note that this is used as an example of how to use the options parameter, 
  -- but is not an option that is usually set.
  v_options := sys.mgw_properties(sys.mgw_property('MQ_SendExit',
                                                   'mySendExit'));
  dbms_mgwadm.create_msgsystem_link(
      linkname => 'mqlink', agent_name=>'default_agent', properties => v_prop, 
      options => v_options );
END;

Creating a WebSphere MQ JMS Link

A WebSphere MQ JMS link is created by calling DBMS_MGWADM.CREATE_MSGSYSTEM_LINK with the following information provided:

• Interface type

  Java Message Service (JMS) distinguishes between queue and topic connections. The Sun Microsystem JMS 1.1 standard supports domain unification that allows both JMS queues and topics to be accessed by a single JMS connection:

  • A WebSphere MQ JMS link created with interface type DBMS_MGWADM.JMS_CONNECTION can be used to access both JMS queues and topics. This is the recommended interface for a WebSphere MQ JMS link.

  • A WebSphere MQ JMS link created with interface type DBMS_MGWADM.JMS_QUEUE_CONNECTION can be used to access only JMS queues.

  • A WebSphere MQ JMS link created with interface type DBMS_MGWADM.JMS_TOPIC_CONNECTION can be used to access only JMS topics.

• WebSphere MQ connection information:

  • Host name and port number of the WebSphere MQ server

  • Queue manager name

  • Channel name

  • User name and password

• Maximum number of messaging connections allowed

  A messaging connection is mapped to a JMS session.

• Log destination (JMS queue or JMS topic) for inbound and outbound propagation

  The log destination type must be valid for the link type. JMS unified links and JMS queue links must use JMS queues for log destinations, and JMS topic links must use topics:

  • For a WebSphere MQ JMS unified or queue link, the log queue name must be the name of a physical WebSphere MQ JMS queue created using WebSphere MQ administration tools.

  • For a WebSphere MQ JMS topic link, the log topic name must be the name of a WebSphere MQ JMS topic. The physical WebSphere MQ queue used by that topic must be created using WebSphere MQ administration tools. By default, the physical queue used is SYSTEM.JMS.D.SUBSCRIBER.QUEUE. A link option can be used to specify a different physical queue.

• Optional information such as:

  • Send, receive, and security exits

  • Character sets

  • WebSphere MQ publish/subscribe configuration used for JMS topics

Example 19-8 configures a Messaging Gateway link to a WebSphere MQ queue manager using a JMS topic interface. The link is named mqjmslink and is configured to use the WebSphere MQ queue manager my.queue.manager on host myhost.mydomain and port 1414, using WebSphere MQ channel mychannel.

This example also uses the options parameter to specify a nondefault durable subscriber queue to be used with the log topic. The Messaging Gateway agent myagent is responsible for the link and all propagation jobs using the link.

DECLARE
  v_options sys.mgw_properties;
  v_prop sys.mgw_mqseries_properties;
BEGIN
  v_prop := sys.mgw_mqseries_properties.construct();
  v_prop.max_connections := 1;
  
  v_prop.interface_type := DBMS_MGWADM.JMS_TOPIC_CONNECTION;
  v_prop.username := 'mqm';
  v_prop.password := 'mqm';
  v_prop.hostname := 'myhost.mydomain';
  v_prop.port     := 1414;
  v_prop.channel  := 'mychannel';
  v_prop.queue_manager := 'my.queue.manager'; 
  
  v_prop.outbound_log_queue := 'mylogtopic' 
  
  -- Specify a WebSphere MQ durable subscriber queue to be used with the
  -- log topic.
  v_options := sys.mgw_properties(
  sys.mgw_property('MQ_JMSDurSubQueue', 'myDSQueue'));
  
  DBMS_MGWADM.CREATE_MSGSYSTEM_LINK(
      linkname     =>  'mqjmslink', 
      agent_name   =>  'myagent',
      properties   =>   v_prop, 
      options      =>   v_options );
END;

Creating a WebSphere MQ Link to Use SSL

Messaging Gateway allows SSL support for IBM WebSphere MQ and WebSphere MQ JMS connections. This section describes how to configure Messaging Gateway to use SSL for a WebSphere MQ Base Java link and the same information applies to a WebSphere MQ JMS link. There are no differences in terms of the Messaging Gateway configuration.

The following are needed in order to use SSL for WebSphere MQ connections:

• A WebSphere MQ channel configured to use SSL.

• A truststore and optionally a keystore file that are in a location accessible to the Messaging Gateway agent process. In an Oracle RAC environment, these files must be accessible to all instances on which the Messaging Gateway agent process might run, using the same path specification.

• Use DBMS_MGWADM.CREATE_MSGSYSTEM_LINK to create a WebSphere MQ link with the desired SSL related link options. At minimum, the MQ_SSLCIPHERSUITE property should be set to specify the SSL ciphersuite used by the channel.

• Use DBMS_MGWADM.SET_OPTION to set certain JSSE Java properties for the Messaging Gateway agent assigned to the link.

JSEE related properties:

• java.net.ssl.keyStore

  This property is used to specify the location of the keystore. A keystore is a database of key material used for various purposes, including authentication and data integrity.

• java.net.ssl.keyStorePassword

  This property is used to specify the password of the keystore. This password is used to check the integrity of the data in the keystore before accessing it.

• java.net.ssl.trustStore

  This property is used to specify the location of the truststore. A truststore is a keystore that is used when making decisions about which clients and servers are trusted.

• java.net.ssl.trustStorePassword

  This property is used to specify the password of the truststore. This password is used to check the integrity of the data in the truststore before accessing it.

The java.net.ssl.keyStore and java.net.ssl.keyStorePassword properties are only needed if the WebSphere MQ channel is configured to use SSL client authentication.

Example 19-9 configures a WebSphere MQ Base Java link mqssllink to use SSL connections using the SSL_RSA_WITH_RC4_128_MD5 ciphersuite. It assumes the channel has been configured for SSL client authentication so the Messaging Gateway agent associated with the link, DEFAULT_AGENT, is configured with Java properties for both a keystore and a truststore.

This configuration should be done when the Messaging Gateway agent is shut down since the Java properties set by DBMS_MGWADM.SET_OPTION are set only when the agent first starts. If the agent is running when the configuration is done it will need to be shutdown and restarted before the SSL connections will be used.

DECLARE
  v_options sys.mgw_properties;
  v_prop sys.mgw_mqseries_properties;
  v_agent varchar2(30) := 'default_agent';
BEGIN
     v_prop := sys.mgw_mqseries_properties.construct();
     v_prop.interface_type := DBMS_MGWADM.MQSERIES_BASE_JAVA_INTERFACE;
     v_prop.max_connections := 1;
     v_prop.username := 'mqm';
     v_prop.password := 'mqm';
     v_prop.hostname := 'myhost.mydomain';
     v_prop.port := 1414;
     v_prop.channel := 'mysslchannel';
     v_prop.queue_manager := 'my.queue.manager';
     v_prop.outbound_log_queue := 'mylogq';
    
   -- specify the SSL ciphersuite
     v_options := sys.mgw_properties(
        sys.mgw_property('MQ_SSLCIPHERSUITE','SSL_RSA_WITH_RC4_128_MD5') );
 
     -- create the MQSeries link
    DBMS_MGWADM.CREATE_MSGSYSTEM_LINK(linkname => 'mqssllink', 
                                    agent_name => v_agent, 
                                    properties => v_prop, 
                                    options => v_options);
 
   -- set Java properties for the agent that specify the JSSE security
   -- properties for the keystore and truststore; the paths will be 
   -- saved as cleartext and the passwords encrypted
 
   DBMS_MGWADM.SET_OPTION(target_type  => DBMS_MGWADM.AGENT_JAVA_PROP,
                       target_name  => v_agent,
                       option_name  => 'javax.net.ssl.keyStore',
                       option_value => '/tmp/mq_ssl/key.jks',
                       encrypted    => false);

   DBMS_MGWADM.SET_OPTION(target_type  => DBMS_MGWADM.AGENT_JAVA_PROP,
                       target_name  => v_agent,
                       option_name  => 'javax.net.ssl.keyStorePassword',
                       option_value => 'welcome',
                       encrypted    => true);

   DBMS_MGWADM.SET_OPTION(target_type  => DBMS_MGWADM.AGENT_JAVA_PROP,
                       target_name  => v_agent,
                       option_name  => 'javax.net.ssl.trustStore',
                       option_value => '/tmp/mq_ssl/trust.jks',
                       encrypted    => false);

   DBMS_MGWADM.SET_OPTION(target_type  => DBMS_MGWADM.AGENT_JAVA_PROP,
                       target_name  => v_agent,
                       option_name  => 'javax.net.ssl.trustStorePassword',
                       option_value => 'welcome',
                       encrypted    => true);
END;

Creating a TIB/Rendezvous Link

A TIB/Rendezvous link is created by calling DBMS_MGWADM.CREATE_MSGSYSTEM_LINK with three parameters (service, network and daemon) for the agent to create a corresponding transport of TibrvRvdTransport type.

A TIB/Rendezvous message system link does not need propagation log queues. Logging information is stored in memory. Therefore, Messaging Gateway can only guarantee at-most-once message delivery.

Example 19-10 configures a TIB/Rendezvous link named rvlink that connects to the rvd daemon on the local computer. An agent name is not specified for the link so the Messaging Gateway default agent (DEFAULT_AGENT) is responsible for the link and all propagation jobs using the link.

DECLARE
  v_options sys.mgw_properties;
  v_prop     sys.mgw_tibrv_properties;
BEGIN
  v_prop := sys.mgw_tibrv_properties.construct();
  
  DBMS_MGWADM.CREATE_MSGSYSTEM_LINK(linkname => 'rvlink', properties => v_prop);
END;

Altering a Messaging System Link

Using DBMS_MGWADM.ALTER_MSGSYSTEM_LINK, you can alter some link information after the link is created. You can alter link information with the Messaging Gateway agent running or shut down. Example 19-11 alters the link mqlink to change the max_connections property.

DECLARE
  v_options sys.mgw_properties;
  v_prop sys.mgw_mqseries_properties;
BEGIN
  -- use alter_construct() for initialization
  v_prop := sys.mgw_mqseries_properties.alter_construct();
  v_prop.max_connections := 2;
  
  DBMS_MGWADM.ALTER_MSGSYSTEM_LINK(
    linkname => 'mqlink', properties => v_prop);
END;

Removing a Messaging System Link

You can remove a Messaging Gateway link to a non-Oracle messaging system with DBMS_MGWADM.REMOVE_MSGSYSTEM_LINK, but only if all registered queues associated with this link have already been unregistered. The link can be removed with the Messaging Gateway agent running or shut down. Example 19-12 removes the link mqlink.

BEGIN
  dbms_mgwadm.remove_msgsystem_link(linkname =>'mqlink');
END;

Views for Messaging System Links

You can use the MGW_LINKS view to check links that have been created. It lists the name and link type, as shown in Example 19-13.

SQL> select link_name, link_type from MGW_LINKS;
 
LINK_NAME     LINK_TYPE 
------------------------
MQLINK        MQSERIES
RVLINK        TIBRV

You can use the MGW_MQSERIES_LINKS and MGW_TIBRV_LINKS views to check messaging system type-specific configuration information, as shown in Example 19-14.

SQL> select link_name, queue_manager, channel, hostname from mgw_mqseries_links;
 
LINK_NAME   QUEUE_MANAGER      CHANNEL     HOSTNAME
----------------------------------------------------------
MQLINK      my.queue.manager  mychannel  myhost.mydomain
 
SQL> select link_name, service, network, daemon from mgw_tibrv_links;
 
LINK_NAME   SERVICE      NETWORK     DAEMON
-----------------------------------------------------
RVLINK 

Registering a Non-Oracle Queue

You can register a non-Oracle queue using DBMS_MGWADM.REGISTER_FOREIGN_QUEUE. Registering a non-Oracle queue provides information for the Messaging Gateway agent to access the queue. However, it does not create the physical queue in the non-Oracle messaging system. The physical queue must be created using the non-Oracle messaging system administration interfaces before the Messaging Gateway agent accesses the queue.

The following information is used to register a non-Oracle queue:

• Name of the messaging system link used to access the queue

• Native name of the queue (its name in the non-Oracle messaging system)

• Domain of the queue

  • DBMS_MGWADM.DOMAIN_QUEUE for a point-to-point queue

  • DBMS_MGWADM.DOMAIN_TOPIC for a publish/subscribe queue

• Options specific to the non-Oracle messaging system

  These options are a set of {name, value} pairs, both of which are strings.

Example 19-15 shows how to register the WebSphere MQ Base Java queue my_mq_queue as a Messaging Gateway queue destq.

BEGIN
  DBMS_MGWADM.REGISTER_FOREIGN_QUEUE(
    name            => 'destq',
    linkname        => 'mqlink',
    provider_queue  => 'my_mq_queue',
    domain          => dbms_mgwadm.DOMAIN_QUEUE);
END;

Unregistering a Non-Oracle Queue

A non-Oracle queue can be unregistered with DBMS_MGWADM.UNREGISTER_FOREIGN_QUEUE, but only if there are no propagation jobs referencing it.

Example 19-16 unregisters the queue destq of the link mqlink.

BEGIN
  DBMS_MGWADM.UNREGISTER_FOREIGN_QUEUE(name =>'destq', linkname=>'mqlink');
END;

View for Registered Non-Oracle Queues

You can use the MGW_FOREIGN_QUEUES view to check which non-Oracle queues are registered and what link each uses, as shown in Example 19-17.

SELECT name, link_name, provider_queue FROM MGW_FOREIGN_QUEUES;
 
NAME   LINK_NAME   PROVIDER_QUEUE
------------------------------------
DESTQ  MQLINK      my_mq_queue

Propagation Job Overview

A propagation job specifies what messages are propagated and how the messages are propagated.

Messaging Gateway allows bidirectional message propagation. An outbound propagation moves messages from Oracle Database Advanced Queuing to non-Oracle messaging systems. An inbound propagation moves messages from non-Oracle messaging systems to Oracle Database Advanced Queuing.

If the propagation source is a queue (point-to-point), then the Messaging Gateway agent moves all messages from the source queue to the destination queue. If the propagation source is a topic (publish/subscribe), then the Messaging Gateway agent creates a subscriber of the propagation source queue in the messaging system. The agent only moves messages that are published to the source queue after the subscriber is created.

When propagating a message, the Messaging Gateway agent converts the message from the format in the source messaging system to the format in the destination messaging system. Users can customize the message conversion by providing a message transformation. If message conversion fails, then the message will be moved to an exception queue, if one has been provided, so that the agent can continue to propagate messages for the subscriber.

A Messaging Gateway exception queue is different from an Oracle Database Advanced Queuing exception queue. Messaging Gateway moves a message to a Messaging Gateway exception queue when message conversion fails. Oracle Database Advanced Queuing moves a message to an Oracle Database Advanced Queuing exception queue after MAX_RETRIES dequeue attempts on the message.

Messages moved to an Oracle Database Advanced Queuing exception queue may result in irrecoverable failures on the associated Messaging Gateway propagation job. To avoid the problem, the MAX_RETRIES parameter of any Oracle Database Advanced Queuing queue that is used as the propagation source of a Messaging Gateway propagation job should be set to a value much larger than 16.

If the messaging system of the propagation source queue supports message selection, then a message selection rule can be specified for a propagation subscriber. Only messages that satisfy the message selector will be propagated.

Users can also specify propagation job options to control how messages are propagated, such as options for JMS message delivery mode and TIB/Rendezvous queue policies.

The MGW_JOBS view can be used to check the configuration and status of Messaging Gateway propagation jobs.

Creating an Oracle Messaging Gateway Propagation Job

Messaging Gateway propagation jobs are created by DBMS_MGWADM.CREATE_JOB.

If the propagation source for non-JMS propagation is an Oracle Database AQ queue, then the queue can be either a single consumer queue or multiple consumer queue. If it is a multiple consumer queue, Messaging Gateway creates a corresponding Oracle Database AQ subscriber MGW_job_name for the propagation job job_name when DBMS_MGWADM.CREATE_JOB is called.

If the propagation source is a JMS topic, such as an Oracle Java Message Service (Oracle JMS) topic or a WebSphere MQ JMS topic, then a JMS subscriber MGW_job_name is created on the topic in the source messaging system by the Messaging Gateway agent. If the agent is not running, then the subscriber will not be created until the agent is restarted.

If the propagation source is a queue, then only one propagation job can be created using that queue as the propagation source. If the propagation source is a topic, then multiple propagation jobs can be set up using that topic as the propagation source with each propagation job having its own corresponding subscriber on the topic in the messaging system.

Example 19-18 creates Messaging Gateway propagation job job_aq2mq.

BEGIN
   DBMS_MGWADM.CREATE_JOB(
     job_name            =>  'job_aq2mq',
     propagation_type    =>   DBMS_MGWADM.OUTBOUND_PROPAGATION,
     source              =>  'mquser.srcq',
     destination         =>  'deqq@mqlink');
END;

Enabling and Disabling a Propagation Job

A propagation job can be initially enabled or disabled when it is created by DBMS_MGWADM.CREATE_JOB. By default, a job is enabled when it is created. You can use DBMS_MGWADM.ENABLE_JOB to enable a propagation job and DBMS_MGWADM.DISABLE_JOB to disable a job. No propagation processing will occur when the job is disabled.

Example 19-19 enables the propagation for propagation job job_aq2mq.

BEGIN
  DBMS_MGWADM.ENABLE_JOB(job_name => 'job_aq2mq');
END;

Example 19-20 disables the propagation for propagation job job_aq2mq.

BEGIN
  DBMS_MGWADM.DISABLE_JOB(job_name => 'job_aq2mq');
END;

Resetting a Propagation Job

When a problem occurs with a propagation job, the Messaging Gateway agent retries the failed operation up to 16 times in an exponential backoff scheme before the propagation job stops. You can use DBMS_MGWADM.RESET_JOB to reset the failure count to zero to allow the agent to retry the failed operation immediately.

Example 19-21 resets the failure count for propagation job job_aq2mq.

BEGIN
  DBMS_MGWADM.RESET_JOB (job_name => 'job_aq2mq');
END;

Altering a Propagation Job

After a propagation job is created you can alter the selection rule, transformation, exception queue, job options, and poll interval of the job using DBMS_MGWADM.ALTER_JOB. The job can be altered with the Messaging Gateway running or shut down.

Example 19-22 adds an exception queue for a propagation job.

BEGIN
    DBMS_MGWADM.ALTER_JOB(
       job_name         =>  'job_aq2mq',        exception_queue  =>  'mgwuser.my_ex_queue');
END;

Example 19-23 changes the polling interval for a propagation job. The polling interval determines how soon the agent can discover the available messages in the propagation source queue. The default polling interval is 5 seconds or the value set for oracle.mgw.polling_interval in the Messaging Gateway initialization file.

BEGIN
    DBMS_MGWADM.ALTER_JOB(
        job_name       =>  'job_aq2mq',         poll_interval  =>  2);
END;

Removing a Propagation Job

You can remove a Messaging Gateway propagation job by calling DBMS_MGWADM.REMOVE_JOB.

Before removing the propagation job from the Messaging Gateway configuration, Messaging Gateway does the following cleanup:

• Removes from the messaging system the associated subscriber that may have been created by Messaging Gateway

• Removes propagation log records from log queues for the job being removed

Messaging Gateway may fail to do the cleanup because:

• The Messaging Gateway agent is not running

• Non-Oracle messaging system is not running

• The Messaging Gateway agent cannot interact with the source or destination messaging system

If the Messaging Gateway cleanup fails for any reason, then the propagation job being removed is placed in a DELETE_PENDING state. The Messaging Gateway agent tries to clean up propagation jobs in a DELETE_PENDING state when:

• DBMS_MGWADM.REMOVE_JOB is called and the Messaging Gateway agent is running.

• The Messaging Gateway agent is starting and finds a propagation job in a DELETE_PENDING state.

DBMS_MGWADM.REMOVE_JOB has a force parameter that allows you to force the propagation job to be removed from the Messaging Gateway configuration without placing it in DELETE_PENDING state. This is useful in case of cleanup failures or if you want to remove a propagation job when the Messaging Gateway agent is not running.

Forcing a propagation job to be removed may result in obsolete log records being left in the log queues, and subscriptions in the messaging systems that may cause unnecessary message accumulation. Oracle recommends that the force option not be used for DBMS_MGWADM.REMOVE_JOB if possible.

Example 19-24 removes a propagation job in a non-forced manner.

BEGIN
    DBMS_MGWADM.REMOVE_JOB (job_name  =>  'job_aq2mq');
END;

Propagation Job, Subscriber, Schedule Interface Interoperability

The user can create two types of propagation jobs, a new style job or an old style job. A new style job is created by DBMS_MGWADM.CREATE_JOB. An old style job is created by calling DBMS_MGWADM.ADD_SUBSCRIBER and DBMS_MGWADM.SCHEDULE_PROPAGATION using the same {propagation_type, source, destination} triplet. A subscriber that does not have a matching schedule, or a schedule that does not have a matching subscriber, is not considered to be a propagation job.

For new style job, the job name will serve as both the subscriber ID and the schedule ID. For an old style job, the subscriber ID is used as the job name.

Both the propagation job subprograms and the subscriber/schedule subprograms can be used for old style propagation jobs. Oracle recommends that you use the job subprograms to create and manage propagation jobs. The job subprograms cannot be used for an unmatched subscriber or schedule since those do not constitute a propagation job.

Only the new job subprograms can be used for new style propagation jobs. An error will occur if a user tries to call a subscriber or scheduler procedure on a new style job.

Other than DBMS_MGWADM.REMOVE_JOB, calling the job subprograms for an old style job is straightforward and the results are effectively the same as calling the corresponding subscriber/schedule subprograms. There may be certain restrictions in the future but there are none at this time.

The DBMS_MGWADM.REMOVE_JOB procedure can be used to remove both new style and old style jobs. A forced and non-forced remove is supported. If the Messaging Gateway agent is not running when a non-forced remove is done, the job will be flagged as delete pending and neither the underlying subscriber nor schedule will be removed at that time. The job (subscriber /schedule pair) will be removed once the agent is restarted and performs its cleanup work or a forced DBMS_MGWADM.REMOVE_JOB is performed. In order to insure that the subscriber/schedule pair is removed at the same time, an error will occur if you first call DBMS_MGWADM.REMOVE_JOB and subsequently attempt to call DBMS_MGWADM.REMOVE_SUBSCRIBER or DBMS_MGWADM.UNSCHEDULE_PROPAGATION for an old style job.

Once DBMS_MGWADM.REMOVE_JOB as been called for a job and it has been flagged as delete pending, all job procedures, other than DBMS_MGWADM.REMOVE_JOB, will fail for both new style and old style jobs. In addition, all subscriber and schedule subprograms will fail if the propagation job happens to be an old style job.DBMS_MGWADM.REMOVE_SUBSCRIBER and DBMS_MGWADM.UNSCHEDULE_PROPAGATION can be used for an old style job as long as DBMS_MGWADM.REMOVE_JOB has not been called for that job. If DBMS_MGWADM.UNSCHEDULE_PROPAGATION is called for an old style job, the schedule is immediately removed and it ceases to be a propagation job and DBMS_MGWADM.REMOVE_SUSCRIBER must be used to remove the subscriber. If DBMS_MGWADM.REMOVE_SUBSCRIBER is called for an old style job, the user can subsequently call DBMS_MGWADM.REMOVE_JOB as long as the subscriber exists.

Propagation Job, Subscriber, Schedule Views

The MGW_JOBS view shows information for the current propagation jobs, both new style jobs and old style jobs, and includes all the pertinent information shown by the MGW_SUBSCRIBERS and MGW_SCHEDULES views. The MGW_SUBSCRIBERS and MGW_SCHEDULES views are still useful for finding an unmatched subscriber or schedule since they don't constitute a propagation job and will not show up in the MGW_JOBS view.

Single Consumer Queue as Propagation Source

Messaging Gateway allows an Oracle Database AQ multiple consumer queue or a single consumer queue to be a propagation source for an outbound new style job created by DBMS_MGWADM.CREATE_JOB. A multiple consumer queue must be used for the propagation source for an outbound old style job. An error will occur if an administrator attempts to call DBMS_MGWADM.ADD_SUBSCRIBER and the source is a single consumer queue.

An Oracle Database AQ dequeue condition is not supported for native (non-JMS) outbound propagation when the propagation source is a single consumer queue.

WebSphere MQ System Properties

Table 19-2 summarizes the basic configuration properties for a WebSphere MQ messaging link. The table indicates which properties of SYS.MGW_MQSERIES_PROPERTIES are optional (NULL allowed), which can be altered, and if alterable, which values can be dynamically changed.

Notes on Table 19-2

1. If hostname is NULL, then the port and channel must be NULL. If the hostname is not NULL, then the port must be not NULL. If the hostname is NULL, then a WebSphere MQ bindings connection is used; otherwise a client connection is used.

2. If interface_type is NULL, then a default value of DBMS_MGWADM.MQSERIES_BASE_JAVA_INTERFACE is used.

3. If max_connections is NULL, then a default value of 1 is used.

4. Attribute inbound_log_queue can be NULL if the link is not used for inbound propagation. The log queue can be altered only when no inbound propagation job references the link.

5. Attribute outbound_log_queue can be NULL if the link is not used for outbound propagation. The log queue can be altered only when no outbound propagation job references the link.

6. The channel attribute must be NULL if a client channel definition table (CCDT) is used. The MQ_ccdtURL link option can be used to specify a CCDT.

Table 19-3 summarizes the optional configuration properties supported when a WebSphere MQ Base Java interface is used to access the WebSphere MQ messaging system. Table 19-4 summarizes the optional configuration properties supported when a WebSphere MQ JMS interface is used. Each table lists the property name, where that property applies, whether the property can be altered, and if alterable, whether the value can be dynamically changed. Only the properties listed in the tables are supported, and any extra properties are ignored.

TIB/Rendezvous System Properties

Table 19-5 summarizes the basic configuration properties for a TIB/Rendezvous messaging link. It indicates which properties of SYS.MGW_TIBRV_PROPERTIES are optional (NULL allowed), which can be altered, and if alterable, which values can be dynamically changed.

Notes on Table 19-5:

1. System default values will be used if service, daemon, or network are NULL.

2. The cm_name and cm_ledger attributes are reserved for future use when TIB/Rendezvous certified messages are supported. At present, a NULL must be specified for these parameters when a TIB/Rendezvous link is configured.

Table 19-6 summarizes the optional configuration properties supported when a TIB/Rendezvous messaging system is used. The table lists the property name, where that property applies, whether the property can be altered, and if alterable, whether the value can be dynamically changed. Only the properties listed in the table are supported, and any extra properties will be ignored.

Optional Link Configuration Properties

This section describes optional link properties you can specify using the options parameter of DBMS_MGWADM.CREATE_MSGSYSTEM_LINK and DBMS_MGWADM.ALTER_MSGSYSTEM_LINK. Each listing also indicates which messaging system might use that property.

MQ_BrokerControlQueue

This property is used by WebSphere MQ JMS. It specifies the name of the broker control queue and corresponds to WebSphere MQ JMS administration tool property BROKERCONQ. The WebSphere MQ default is SYSTEM.BROKER.CONTROL.QUEUE.

MQ_BrokerPubQueue

This property is used by WebSphere MQ JMS. It specifies the name of the broker publish queue and corresponds to WebSphere MQ JMS administration tool property BROKERPUBQ. The WebSphere MQ default is SYSTEM.BROKER.DEFAULT.STREAM.

MQ_BrokerQueueManager

This property is used by WebSphere MQ JMS. It specifies the name of the broker queue manager and corresponds to WebSphere MQ administration tool property BROKERQMGR. If it is not set, then no default is used.

MQ_BrokerVersion

This property is used by WebSphere MQ JMS. It specifies the broker version number and corresponds to WebSphere MQ JMS administration tool property BROKERVER. The WebSphere MQ default is 0.

MQ_ccdtUrl

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the URL string of a client channel definition table (CCDT) to be used. If not set, a CCDT is not used. If a CCDT is used, then the SYS.MGW_MQSERIES_PROPERTIES.channel link property must be NULL.

MQ_ccsid

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the character set identifier to be used to translate information in the WebSphere MQ message header. This should be the integer value of the character set (for example, 819) rather than a descriptive string. If it is not set, then the WebSphere MQ default character set 819 is used.

MQ_JmsDurSubQueue

This property is used by WebSphere MQ JMS. It applies to WebSphere MQ JMS topic links only. The SYS.MGW_MQSERIES_PROPERITES attributes, inbound_log_queue and outbound_log_queue, specify the names of WebSphere MQ JMS topics used for propagation logging. This property specifies the name of the WebSphere MQ queue from which durable subscription messages are retrieved by the log topic subscribers. The WebSphere MQ default queue is SYSTEM.JMS.D.SUBSCRIBER.QUEUE.

MQ_PubAckInterval

This property is used by WebSphere MQ JMS. It specifies the interval, in number of messages, between publish requests that require acknowledgment from the broker and corresponds to WebSphere MQ JMS administration tool property PUBACKINT. The WebSphere MQ default is 25.

MQ_ReceiveExit

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the fully qualified Java classname of a class implementing the MQReceiveExit interface. This class must be in the CLASSPATH of the Messaging Gateway agent. There is no default.

MQ_ReceiveExitInit

This initialization string is used by WebSphere MQ JMS. It is passed by WebSphere MQ JMS to the constructor of the class specified by MQ_ReceiveExit and corresponds to WebSphere MQ JMS administration tool property RECEXITINIT. There is no default.

MQ_SecurityExit

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the fully qualified Java classname of a class implementing the MQSecurityExit interface. This class must be in the CLASSPATH of the Messaging Gateway agent. There is no default.

MQ_SecurityExitInit

This initialization string is used by WebSphere MQ JMS. It is passed by WebSphere MQ JMS to the constructor of the class specified by MQ_SecurityExit and corresponds to WebSphere MQ JMS administration tool property SECEXITINIT. There is no default.

MQ_SendExit

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the fully qualified Java classname of a class implementing the MQSendExit interface. This class must be in the CLASSPATH of the Messaging Gateway agent. There is no default.

MQ_SendExitInit

This initialization string is used by WebSphere MQ JMS. It is passed by WebSphere MQ JMS to the constructor of the class specified by MQ_SendExit. It corresponds to WebSphere MQ JMS administration tool property SENDEXITINIT. There is no default.

MQ_SSLCipherSuite

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the CipherSuite to be used; for example, SSL_RSA_WITH_RC4_128_MD5. This corresponds to the WebSphere MQ SSLCIPHERSUITE administration property.

MQ_SSLCrl

This property is used by WebSphere MQ JMS. It specifies a space-delimited list of LDAP servers that can be used for certificate revocation list (CRL) checking. If not set, no CRL checking is done. This corresponds to the WebSphere MQ SSLCRL administration property. This option is not supported for WebSphere MQ Base Java, and instead, a client channel definition table (CCDT) must be used if CRL checking is needed.

MQ_SSLFipsRequired

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It indicates whether the CipherSuite being used is supported by the IBM Java JSSE FIPS provider (IBMSJSSEFIPS). The value should be TRUE or FALSE. The default value is FALSE. This corresponds to the WebSphere MQ SSLFIPSREQUIRED administration property.

MQ_SSLPeerName

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies a distinguished name (DN) pattern that the queue manager certificate must match in order for a connection to be established. If not set, no DN check is performed. This corresponds to the WebSphere MQ SSLPEERNAME administration property.

MQ_SSLResetCount

This property is used by WebSphere MQ Base Java and WebSphere MQ JMS. It specifies the total number of bytes sent and received before the secret key is renegotiated. If not set, the key is not renegotiated. This corresponds to the WebSphere MQ SSLRESETCOUNT administration property.

Optional Foreign Queue Configuration Properties

This section describes optional foreign queue properties that you can specify using the options parameter of DBMS_MGWADM.REGISTER_FOREIGN_QUEUE. Each listing also indicates which messaging system might use that property.

MQ_CharacterSet

This property is used by WebSphere MQ JMS. It is used only for outbound propagation to a JMS queue or topic. It specifies the character set to be used to encode text strings sent to the destination. It should be the integer value of the character set (for example, 1208) rather than a descriptive string. The default value used by Messaging Gateway is 1208 (UTF8).

MQ_JmsDurSubQueue

This property is used by WebSphere MQ JMS. It is a string representing the name of the WebSphere MQ queue from which durable subscription messages are retrieved by subscribers on this topic. It applies only to WebSphere MQ JMS topics. The WebSphere MQ default queue is SYSTEM.JMS.D.SUBSCRIBER.QUEUE.

MQ_JmsTargetClient

This property is used by WebSphere MQ JMS. It is used only for outbound propagation to a JMS queue or topic. Supported values are TRUE and FALSE. TRUE indicates that WebSphere MQ should store the message as a JMS message. FALSE indicates that WebSphere MQ should store the message in non-JMS format so that non-JMS applications can access it. Default is TRUE.

MQ_openOptions

This property is used by WebSphere MQ Base Java. It specifies the value used for the openOptions argument of the WebSphere MQ Base Java MQQueueManager.accessQueue method. No value is required. But if one is given, then the Messaging Gateway agent adds MQOO_OUTPUT to the specified value for an enqueue (put) operation. MQOO_INPUT_SHARED is added for a dequeue (get) operation. The default is MQOO_OUTPUT for an enqueue/put operation; MQOO_INPUT_SHARED for a dequeue/get operation.

Optional Job Configuration Properties

This section describes optional propagation job properties that you can specify using the options parameter of DBMS_MGWADM.CREATE_JOB and DBMS_MGWADM.ALTER_JOB.

AQ_MsgProperties

This property is used by TIB/Rendezvous. It specifies how Oracle Database AQ message properties will be used during message propagation. Supported values are TRUE and FALSE. The default value is FALSE.

For an outbound propagation job, if the value is TRUE (case insensitive), then the Messaging Gateway agent will add a field for most Oracle Database AQ message properties to the message propagated to the TIB/Rendezvous subject.

For an inbound propagation job, if the value is TRUE (case insensitive), then the Messaging Gateway agent will search the source message for a field with a reserved name, and if it exists, use its value to set the corresponding Oracle Database AQ message property. A default value will be used if the field does not exist or does not have an expected datatype.

JMS_DeliveryMode

This property is used by WebSphere MQ JMS and Oracle JMS. You can use this property when the propagation destination is a JMS messaging system. It sets the delivery mode of messages enqueued to the propagation destination queue by a JMS MessageProducer. The default is PRESERVE_MSG. Supported values and their associated delivery modes are:

• PERSISTENT (DeliveryMode.PERSISTENT)

• NON_PERSISTENT (DeliveryMode.NON_PERSISTENT)

• PRESERVE_MSG (delivery mode of the source JMS message is used)

JMS_NoLocal

This property is used by WebSphere MQ JMS and Oracle JMS. You can use it when the propagation source is a JMS messaging system. It sets the noLocal parameter of a JMS TopicSubscriber. TRUE indicates that messages that have been published to this topic through the same Messaging Gateway link will not be propagated. The default value FALSE indicates that such messages will be propagated from the topic.

MsgBatchSize

This property can be used by any supported messaging system. It specifies the maximum number of messages, if available, to be propagated in one transaction. The default is 30.

PreserveMessageID

This property is used by WebSphere MQ Base Java, WebSphere MQ JMS, TIB/Rendezvous, and Oracle JMS. It specifies whether Messaging Gateway should preserve the original message identifier when the message is propagated to the destination messaging system. The exact details depend on the capabilities of the messaging systems involved. Supported values are TRUE and FALSE. The default value is FALSE.

RV_discardAmount

This property is used by TIB/Rendezvous. It specifies the discard amount of a queue. It is meaningful only for an inbound propagation job. The default is 0.

RV_limitPolicy

This property is used by TIB/Rendezvous. It specifies the limit policy for resolving overflow of a queue limit. It is meaningful only for an inbound propagation job. The default is DISCARD_NONE. Supported values and their associated limit policies are: DISCARD_NONE, DISCARD_FIRST, DISCARD_LAST and DISCARD_NEW.

• DISCARD_NONE (TibrvQueue.DISCARD_NONE)

• DISCARD_FIRST (TibrvQueue.DISCARD_FIRST)

• DISCARD_LAST (TibrvQueue.DISCARD_LAST)

• DISCARD_NEW (TibrvQueue.DISCARD_NEW)

RV_maxEvents

This property is used by TIB/Rendezvous. It specifies the maximum event limit of a queue. It is meaningful only for an inbound propagation job. The default is 0.