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Oracle® Streams Advanced Queuing User's Guide
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18 Getting Started with Oracle Messaging Gateway

This chapter describes Oracle Messaging Gateway (MGW) prerequisites and how to load, set up, and unload Messaging Gateway. It also describes how to set up and modify the mgw.ora initialization file.

This chapter contains these topics:

18.1 Oracle Messaging Gateway Prerequisites

Messaging Gateway uses one Oracle Scheduler job for each Messaging Gateway agent. If the value of the JOB_QUEUE_PROCESSES database initialization parameter is zero, then that parameter does not influence the number of Oracle Scheduler jobs that can run concurrently. However, if the value is non-zero, it effectively becomes the maximum number of Scheduler jobs and job queue jobs than can run concurrently. If a non-zero value is set, it should be large enough to accommodate a Scheduler job for each Messaging Gateway agent to be started.

18.2 Loading and Setting Up Oracle Messaging Gateway

Perform the following procedures before running Messaging Gateway:

18.2.1 Loading Database Objects into the Database

Using SQL*Plus, run ORACLE_HOME/mgw/admin/catmgw.sql as user SYS as SYSDBA. This script loads the database objects necessary for Messaging Gateway, including roles, tables, views, object types, and PL/SQL packages. It creates public synonyms for Messaging Gateway PL/SQL packages. It creates two roles, MGW_ADMINISTRATOR_ROLE and MGW_AGENT_ROLE, with certain privileges granted. All objects are owned by SYS.

18.2.2 Modifying listener.ora for the External Procedure

This procedure is for Linux 32-bit operating systems only. Static service information for the listener is not necessary on the Windows operating system.

You must modify listener.ora so that the Messaging Gateway PL/SQL packages can call the external procedure.

  1. Verify that the default Inter-process Communication (IPC) protocol address for the external procedures is set.

    LISTENER = (ADDRESS_LIST=
    (ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC))
    
    
  2. Add static service information for the listener in step 1. This involves setting a SID_DESC for the listener. Within the SID_DESC, the parameters described in Table 18-1 are important to Messaging Gateway and must be specified according to your own situation.

Table 18-1 SID_DESC Parameters

Parameter Description
SID_NAME The SID that is specified in the net service name in tnsnames.ora. In the following example, the SID_NAME is mgwextproc.
ENVS Set up the LD_LIBRARY_PATH environment needed for the external procedure to run. The LD_LIBRARY_PATH must contain the following paths:
JRE_HOME/lib/PLATFORM_TYPE
JRE_HOME/lib/PLATFORM_TYPE/server
ORACLE_HOME/lib

It should also contain any additional libraries required by third-party messaging systems. See "Setting Up Non-Oracle Messaging Systems".

ORACLE_HOME Your Oracle home directory. Using $ORACLE_HOME does not work.
PROGRAM The name of the external procedure agent, which is extproc


Note:

JRE_HOME represents the root directory of a JRE installation, just as ORACLE_HOME represents the root directory of an Oracle installation. Oracle recommends that you use the JRE installed with Oracle Database.

Example 18-1 adds SID_NAME mgwextproc to a listener.ora file for Linux x86.

Example 18-1 Adding Static Service Information for a Listener

# Add a SID_DESC
SID_LIST_LISTENER= (SID_LIST=
(SID_DESC =
   (SID_NAME= mgwextproc)
   (ENVS=
     "LD_LIBRARY_PATH=JRE_HOME/lib/i386:JRE_HOME/lib/i386/server:ORACLE_HOME/lib")
   (ORACLE_HOME=ORACLE_HOME)
   (PROGRAM = extproc))

18.2.3 Modifying tnsnames.ora for the External Procedure

This procedure is for Linux 32-bit operating systems only. For the external procedure, configure a net service name MGW_AGENT in tnsnames.ora whose connect descriptor matches the information configured in listener.ora, as shown in Example 18-2. The net service name must be MGW_AGENT (this value is fixed). The KEY value must match the KEY value specified for the IPC protocol in listener.ora. The SID value must match the value specified for SID_NAME of the SID_DESC entry in listener.ora.

Example 18-2 Configuring MGW_AGENT

MGW_AGENT = 
(DESCRIPTION= 
   (ADDRESS_LIST= (ADDRESS= (PROTOCOL=IPC)(KEY=EXTPROC))) 
   (CONNECT_DATA= (SID=mgwextproc)))

Note:

If the names.default_domain parameter for sqlnet.ora has been used to set a default domain, then that domain must be appended to the MGW_AGENT net service name in tnsnames.ora. For example, if sqlnet.ora contains the entry names.default_domain=acme.com, then the net service name in tnsnames.ora must be MGW_AGENT.acme.com.

18.2.4 Setting Up a mgw.ora Initialization File

The Messaging Gateway default initialization file ORACLE_HOME/mgw/admin/mgw.ora is a text file. The Messaging Gateway external procedure uses it to get initialization parameters to start the Messaging Gateway agent. Copy ORACLE_HOME/mgw/admin/sample_mgw.ora to mgw.ora and modify it according to your situation.

The following procedure sets environment variables and other parameters required for all applications of Messaging Gateway:

  1. Windows Operating System Only: Set the MGW_PRE_PATH variable. Its value is the path to the jvm.dll library:

    set MGW_PRE_PATH = JRE_HOME\bin\client
    
    

    This variable is prepended to the path inherited by the Messaging Gateway agent process.

  2. Set CLASSPATH to include at least the following:

    • JRE runtime classes:

      JRE_HOME/lib/rt.jar
      
      
    • Oracle JDBC classes:

      ORACLE_HOME/jdbc/lib/ojdbc5.jar
      
      
    • Oracle internationalization classes:

      ORACLE_HOME/jlib/orai18n.jar
      
      
    • SQLJ runtime:

      ORACLE_HOME/sqlj/lib/runtime12.jar
      
      
    • Java Message Service (JMS) interface

      ORACLE_HOME/rdbms/jlib/jmscommon.jar
      
      
    • Oracle JMS implementation classes

      ORACLE_HOME/rdbms/jlib/aqapi.jar
      
      
    • Java transaction API

      ORACLE_HOME/jlib/jta.jar
      
      
    • Any additional classes needed for Messaging Gateway to access non-Oracle messaging systems


      Note:

      Replace ORACLE_HOME with the appropriate, spelled-out value. Using $ORACLE_HOME, for example, does not work.

      Users of the Windows operating system must set CLASSPATH using the Windows operating system path syntax.


18.2.5 Creating an Oracle Messaging Gateway Administration User

To perform Messaging Gateway administration work, a database user must be created with MGW_ADMINISTRATOR_ROLE privileges, as shown in Example 18-3.

Example 18-3 Creating a Messaging Gateway Administrator User

CREATE USER admin_user IDENTIFIED BY admin_password;
GRANT CREATE SESSION to admin_user;
GRANT MGW_ADMINISTRATOR_ROLE to admin_user;

18.2.6 Creating an Oracle Messaging Gateway Agent User

To establish the Messaging Gateway agent connection back to the database, a database user with MGW_AGENT_ROLE privileges must be created, as shown in Example 18-4.

Example 18-4 Creating a Messaging Gateway Agent User

CREATE USER agent_user IDENTIFIED BY agent_password;
GRANT CREATE SESSION to agent_user;
GRANT MGW_AGENT_ROLE to agent_user;

18.2.7 Configuring Oracle Messaging Gateway Connection Information

After the Messaging Gateway agent user is created, the administration user uses DBMS_MGWADM.ALTER_AGENT to configure Messaging Gateway with the username, password, and database connect string used by the Messaging Gateway agent to connect back to the database, as shown in Example 18-5. Use the Messaging Gateway username and password that you created in "Creating an Oracle Messaging Gateway Agent User". The database connect string parameter can be set to either a net service name in tnsnames.ora (with IPC protocol for better performance) or NULL. If NULL, then the oracle_sid parameter must be set in mgw.ora.

For this release, always specify a not NULL value for the database connect string parameter when calling DBMS_MGWADM.ALTER_AGENT.

Example 18-5 Configuring Messaging Gateway Connection Information

set echo off
set verify off
connect admin_user
 
ACCEPT password CHAR PROMPT 'Enter the password for AGENT_USER: ' HIDE

EXEC DBMS_MGWADM.ALTER_AGENT(
      agent_name  => 'default_agent', 
      username    => 'agent_user', 
      password    => '&password', 
      database    => 'agent_database');

18.2.8 Configuring Oracle Messaging Gateway in a RAC Environment

This section contains these topics:

18.2.8.1 Configuring Connection Information for the MGW Agent Connections

You must make all database connections made by the Messaging Gateway agent to the instance on which the Messaging Gateway agent process is running. This ensures correct failover behavior in a Real Application Clusters (RAC) environment. You can configure connections this way by having the instances use slightly different tnsnames.ora files. Each file contains an entry with the same net service name, but the connect data refers to only the instance associated with that tnsnames.ora file. The common net service name would then be used for the database parameter when DBMS_MGWADM.ALTER_AGENT is used to configure the Messaging Gateway agent database connection information.

For example, in a two-instance RAC environment with instances OraDB1 and OraDB2, where the net service name AGENT_DB is to be used, the tnsnames.ora for instance OraDB1 would look like this:

AGENT_DB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = myhost1.mycorp.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = OraDB10.mycorp.com)
      (INSTANCE_NAME = OraDB1)
    )
  )

The tnsnames.ora for OraDB2 would look like this:

AGENT_DB =
  (DESCRIPTION =
    (ADDRESS = (PROTOCOL = TCP)(HOST = myhost2.mycorp.com)(PORT = 1521))
    (CONNECT_DATA =
      (SERVER = DEDICATED)
      (SERVICE_NAME = OraDB10.mycorp.com)
      (INSTANCE_NAME = OraDB2)
    )
  )

You would then configure Messaging Gateway agent user connection information by running the following command:

EXEC DBMS_MGWADM.ALTER_AGENT(
   agent_name   => 'default_agent', 
   username     => 'agent_user', 
   password     => 'agent_password', 
   database     => 'agent_db');

18.2.8.2 Setting the RAC Instance for the Messaging Gateway Agent

Messaging Gateway provides service affinity for the Messaging Gateway agent external process by leveraging the database service support of the Oracle Scheduler. By default, a Messaging Gateway agent will use the default database service that is mapped to all instances. If you want a Messaging Gateway agent to start on a select group of database instances, you must create a database service for those instances and then assign the database service to the Messaging Gateway agent using the SERVICE parameter of the DBMS_MGWADM.CREATE_AGENT or DBMS_MGWADM.ALTER_AGENT procedures. The DBMS_MGWADM.STARTUP procedure submits an Oracle Scheduler job that starts the Messaging Gateway agent external process when the Scheduler job is executed. The Scheduler job will use the database service configured for the Messaging Gateway agent.

The database service specified by the SERVICE parameter is only used for the service affinity of the Oracle Scheduler job and thus the service affinity for the Messaging Gateway external process. It is not used for the database connections made by the Messaging Gateway agent user. Those JDBC client connections are based on the values specified for the DATABASE and CONNTYPE parameters.

18.3 Setting Up Non-Oracle Messaging Systems

This section contains these topics:

18.3.1 Setting Up for TIB/Rendezvous

Running as a TIB/Rendezvous Java client application, the Messaging Gateway agent requires TIB/Rendezvous software to be installed on the computer where the Messaging Gateway agent runs. In this section TIBRV_HOME refers to the installed TIB/Rendezvous software location.

Modifying listener.ora

On the Linux operating system, LD_LIBRARY_PATH in the entry for Messaging Gateway must include TIBRV_HOME/lib for the agent to access TIB/Rendezvous shared library files.

On the Windows operating system, you are not required to modify listener.ora. But the system environment variable PATH must include TIBRV_HOME\bin.

Modifying mgw.ora

MGW_PRE_PATH must include the directory that contains the TIB/Rendezvous license ticket file (tibrv.tkt), which usually is located in TIBRV_HOME/bin.

CLASSPATH must include the TIB/Rendezvous jar file TIBRV_HOME/lib/tibrvj.jar. If you use your own customized TIB/Rendezvous advisory message callback, then the location of the callback class must also be included.

You can set the following Java properties to change the default setting:

Example 18-6 Setting Java Properties

setJavaProp oracle.mgw.tibrv.encoding=ISO8859_1
setJavaProp oracle.mgw.tibrv.intraProcAdvSubjects=_RV.>
setJavaProp oracle.mgw.tibrv.advMsgCallback=MyadvCallback

18.3.2 Setting Up for WebSphere MQ Base Java or JMS

The WebSphere MQ client and WebSphere MQ classes for Java and JMS must be installed on the computer where the Messaging Gateway agent runs. In this section MQ_HOME refers to the location of the installed client. On the Linux operating system, this location is always /opt/mqm. On the Windows operating system, the installed location can vary.

Modifying listener.ora

No extra modification of listener.ora is necessary for Messaging Gateway to access WebSphere MQ.

Modifying mgw.ora

When using WebSphere MQ Base Java (non-JMS) interface, set CLASSPATH to include at least the following (in addition to those in "Setting Up a mgw.ora Initialization File"):

  • MQ_HOME/java/lib/com.ibm.mq.jar

  • MQ_HOME/java/lib/connector.jar

When using WebSphere MQ JMS interface, set CLASSPATH to include at least the following (in addition to those in "Setting Up a mgw.ora Initialization File"):

  • MQ_HOME/java/lib/com.ibm.mqjms.jar

  • MQ_HOME/java/lib/com.ibm.mq.jar

  • MQ_HOME/java/lib/connector.jar

18.4 Verifying the Oracle Messaging Gateway Setup

The following procedure verifies the setup and includes a simple startup and shutdown of the Messaging Gateway agent:

  1. Start the database listeners.

    Start the listener for the external procedure and other listeners for the regular database connection.

  2. Test the database connect string for the Messaging Gateway agent user.

    Run sqlplus agent_user/agent_password@agent_database.

    If it is successful, then the Messaging Gateway agent is able to connect to the database.

  3. Linux Operating System Only: Test the net service entry used to call the external procedure.

    Run sqlplus agent_user/agent_password@MGW_AGENT.

    This should fail with "ORA-28547: connection to server failed, probable Oracle Net admin error". Any other error indicates that the tnsnames.ora, listener.ora, or both are not correct.

  4. Connect as admin_user and call DBMS_MGWADM.STARTUP to start the Messaging Gateway agent.

  5. Using the MGW_GATEWAY view, wait for AGENT_STATUS to change to RUNNING and AGENT_PING to change to REACHABLE.

  6. Connect as admin_user and call DBMS_MGWADM.SHUTDOWN to shut down the Messaging Gateway agent.

  7. Using the MGW_GATEWAY view, wait for AGENT_STATUS to change to NOT_STARTED.

18.5 Unloading Oracle Messaging Gateway

Use this procedure to unload Messaging Gateway:

  1. Shut down Messaging Gateway.

  2. Remove any user-created queues whose payload is a Messaging Gateway canonical type (for example, SYS.MGW_BASIC_MSG_T).

  3. Using SQL*Plus, run ORACLE_HOME/mgw/admin/catnomgw.sql as user SYS as SYSDBA.

    This drops the database objects used by Messaging Gateway, including roles, tables, views, packages, object types, and synonyms.

  4. Remove entries for Messaging Gateway created in listener.ora and tnsnames.ora.

18.6 Understanding the mgw.ora Initialization File

Messaging Gateway reads initialization information from a text file when the Messaging Gateway agent starts. The initialization file contains lines for setting initialization parameters, environment variables, and Java properties. Each entity must be specified on one line. Leading whitespace is trimmed in all cases.

A Messaging Gateway administrator can specify the initialization file to be used for a Messaging Gateway agent via DBMS_MGWADM.CREATE_AGENT and DBMS_MGWADM.ALTER_AGENT. If an initialization file is not specified then a default initialization file will be used.

The default initialization file for the default agent is ORACLE_HOME/mgw/admin/mgw.ora.

The default initialization file for a named agent is ORACLE_HOME/mgw/admin/mgw_AGENTNAME.ora where AGENTNAME is the name in uppercase of the Messaging Gateway agent. For example, if the agent name is my_agent then the name of the agent's default initialization file is ORACLE_HOME/mgw/admin/mgw_MY_AGENT.ora. If the default initialization file for a named agent is not found then ORACLE_HOME/mgw/admin/mgw.ora will be used.

18.6.1 mgw.ora Initialization Parameters

The initialization parameters are typically specified by lines having a "name=value<NL>" format where name represents the parameter name, value represents its value and <NL> represents a new line.

log_directory

Usage:  Specifies the directory where the Messaging Gateway log/trace file is created.

Format:  

log_directory = value

Default: 

ORACLE_HOME/mgw/log

Example:  

log_directory = /private/mgwlog

log_level

Usage:  Specifies the level of logging detail recorded by the Messaging Gateway agent. The logging level can be dynamically changed by changed by calling DBMS_MGWADM.SET_LOG_LEVEL while the Messaging Gateway agent is running. Oracle recommends that log level 0 (the default value) be used at all times.

Format:  

log_level = value

Values:  

0 for basic logging; equivalent to DBMS_MGWADM.BASIC_LOGGING

1 for light tracing; equivalent to DBMS_MGWADM.TRACE_LITE_LOGGING

2 for high tracing; equivalent to DBMS_MGWADM.TRACE_HIGH_LOGGING

3 for debug tracing; equivalent to DBMS_MGWADM.TRACE_DEBUG_LOGGING

Example:  

log_level = 0

18.6.2 mgw.ora Environment Variables

Because the Messaging Gateway process environment is not under the direct control of the user, certain environment variables should be set using the initialization file. The environment variables currently used by the Messaging Gateway agent are CLASSPATH, MGW_PRE_PATH, and ORACLE_SID.

Environment variables such as CLASSPATH and MGW_PRE_PATH are set so the Messaging Gateway agent can find the required shared objects, Java classes, and so on. Environment variables are specified by lines having a "set env_var=value<NL>" or "setenv env_var=value<NL>" format where env_var represents the name of the environment variable to set, value represents the value of the environment variable, and <NL> represents a new line.

CLASSPATH

Usage:  Used by the Java Virtual Machine to find Java classes needed by the Messaging Gateway agent for propagation between Oracle Streams AQ and non-Oracle messaging systems.

Format:  

set CLASSPATH=value

Example:  

set CLASSPATH=ORACLE_HOME/jdbc/lib/ojdbc5.jar:JRE_HOME/lib/rt.jar:
ORACLE_HOME/sqlj/lib/runtime12.jar:ORACLE_HOME/jlib/orai18n.jar:ORACLE_HOME/rdbms/
jlib/jmscommon.jar:ORACLE_HOME/rdbms/jlib/aqapi.jar:ORACLE_HOME/jlib/jta.jar:
/opt/mqm/java/lib/com.ibm.mq.jar:/opt/mqm/java/lib/com.ibm.mqjms.jar:/opt/mqm/java
/lib/connector.jar

MGW_PRE_PATH

Usage:  Appended to the front of the path inherited by the Messaging Gateway process. For the Windows operating system, this variable must be set to indicate where the library jvm.dll is found.

Format:  

set MGW_PRE_PATH=value

Example:  

set MGW_PRE_PATH=JRE_HOME\bin\client

ORACLE_SID

Usage:  Can be used when a service name is not specified when configuring Messaging Gateway.

Format:  

set ORACLE_SID=value

Example: 

set ORACLE_SID=my_sid

18.6.3 mgw.ora Java Properties

You must specify Java system properties for the Messaging Gateway JVM when working with TIB/Rendezvous subjects. You can use the setJavaProp parameter of the Messaging Gateway initialization file for this. Java properties are specified by lines having a "setJavaProp prop_name=value<NL>" format, where prop_name represents the name of the Java property to set, value represents the value of the Java property, and <NL> represents a new line character.

oracle.mgw.batch_size

Usage: This Java property represents the maximum number of messages propagated in one transaction. It serves as a default value if the Messaging Gateway job option, MsgBatchSize, is not specified. If altered from the default, then consideration should be given to the expected message size and the Messaging Gateway agent memory (see max_memory parameter of DBMS_MGWADM.ALTER_AGENT). The minimum value of this Java property is 1, the maximum is 100, and the default is 30.

Syntax: 

setJavaProp oracle.mgw.batch_size=value

Example: 

setJavaProp oracle.mgw.batch_size=10

oracle.mgw.polling_interval

Usage: This parameter specifies the time (in milliseconds) that must elapse between polls for available messages of a propagation source queue. The default polling interval used by Messaging Gateway is 5000 milliseconds (5 seconds).

Syntax: 

setJavaProp oracle.mgw.polling_interval=value 

Example: 

setJavaProp oracle.mgw.polling_interval=1000 

oracle.mgw.tibrv.encoding

Usage: This parameter specifies the character encoding to be used by the TIB/Rendezvous messaging system links. Only one character set for all configured TIB/Rendezvous links is allowed due to TIB/Rendezvous restrictions. The default is ISO 8859-1 or the character set specified by the Java system property file.encoding.

Syntax: 

setJavaProp oracle.mgw.tibrv.encoding=value 

Example: 

setJavaProp oracle.mgw.tibrv.encoding=ISO8859_1 

oracle.mgw.tibrv.intraProcAdvSubjects

Usage Used for all TIB/Rendezvous messaging system links, this parameter specifies the names of system advisory subjects that present on the intraprocess transport.

Syntax 

setJavaProp oracle.mgw.tibrv.intraProcAdvSubjects=
advisorySubjectName[:advisorySubjectName]

Example: 

setJavaProp oracle.mgw.tibrv.intraProcAdvSubjects=_RV.>

oracle.mgw.tibrv.advMsgCallback

Usage: Used for all TIB/Rendezvous messaging system links, this parameter specifies the name of the Java class that implements the TibrvMsgCallback interface to handle system advisory messages. If it is not specified, then the default system advisory message handler provided by Messaging Gateway is used, which writes system advisory messages into Messaging Gateway log files. If it is specified, then the directory where the class file is stored must be included in the CLASSPATH in mgw.ora.

Syntax: 

setJavaProp oracle.mgw.tibrv.advMsgCallback=className

Example: 

setJavaProp oracle.mgw.tibrv.advMsgCallback=MyAdvCallback

oracle.net.tns_admin

Usage: This parameter specifies the directory of the tnsnames.ora file. It must be set if the Messaging Gateway agent is configured to use the JDBC Thin driver and the database specifier of the agent connection information is a TNSNames alias. This does not need to be set if the JDBC OCI driver is used or the database specifier is something other than a TNSNames alias.

Syntax: 

setJavaProp oracle.net.tns_admin=value

Example: 

setJavaProp oracle.net.tns_admin=/myoraclehome/network/admin

18.6.4 mgw.ora Comment Lines

Comment lines are designated with a # character as the first character of the line.