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Oracle AQ Queue Tables and Queues

Oracle Advanced Queuing (AQ) provides the underlying message queuing system used by the iProcess message queues. Each message queue defined in the iql_queues table must be mapped to an AQ queue, which in turn must be stored in an AQ table.

When the iProcess Engine is installed, the init2Kora.sql script (on UNIX, or on Windows init2Kora_tok.sql) creates the default set of AQ tables, queues and object types required by the system (see Default Message Queues and AQ Tables.)

The init2Kora.sql script (on UNIX, or on Windows init2Kora_tok.sql) also creates a non-persistent Oracle AQ queue called sw_system_events. This queue is used to route all iProcess events to the iProcess event manager. (iProcess event management is provided by the Oracle Event Manager on UNIX, and by the iProcess Events COM+ application on Windows.)

If you subsequently decide to add additional message queues, you must use the Oracle DBMS_AQADM package to manually create the Oracle AQ queue tables and queues needed by those message queues. The following sections explain how to do this.

For a detailed description of the DBMS_AQADM package procedures referred to in this section, see the Oracle9i Supplied PL/SQL Packages and Types Reference guide in your Oracle documentation set.

SWLOCALMSG Object Type

An AQ queue table must be associated with one particular message type, which must already exist when you create the AQ queue table.

All AQ queue tables used by the iProcess Engine must use the SWLOCALMSG object type, which is created when the iProcess Engine is installed.

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CREATE TYPE TABLE_OWNER.SWLOCALMSG AS OBJECT (
msginfo VARCHAR2(500),
node varchar2(24),
contenttype number(2),
data VARCHAR2(1000)
);

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AQ Queue Tables

Use the DBMS_AQADM.CREATE_QUEUE_TABLE procedure to create an AQ queue table. The following parameters are required.

Column	Description
queue_table	Unique name of this queue table. This name is used in the queue_phys_descr column of the iql_queues table.
queue_payload_type	Object type of data stored by this queue table. This value must be swlocalmsg.
storage_clause	Tablespace to be used by this queue table. Note: Each queue table can be associated with a different tablespace, which in turn can be associated with a different datafile. Distributing queue tables in this way provides an easy way of reducing I/O contention and optimizing performance. See Appendix B on page 249 for more information.
sort_list	Sort criteria by which messages are sorted in ascending order and dequeued based on this order.
comment	Description of this queue table.
compatible	Lowest database version that this queue table is compatible with. This value must be 8.1.

The following example, from the init2Kora.sql script, shows the SQL used to create one of the default background Mbox tables that is created when the iProcess Engine is installed.

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DBMS_AQADM.CREATE_QUEUE_TABLE (
        queue_table => 'TABLE_OWNER.bgmboxtable1',
        queue_payload_type => 'TABLE_OWNER.swlocalmsg',
        sort_list => ' priority, enq_time',
        storage_clause => 'tablespace AQTABLESPACE',
        comment => 'default background mbox',
        compatible => ’8.1’);

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AQ Queues

To create an AQ queue and make it available to be used as an iProcess message queue:

1.	Use the DBMS_AQADM.CREATE_QUEUE procedure to create the AQ queue. The following parameters are required.

Column	Description
queue_name	Unique name of this queue. This name is used in the queue_phys_descr column of the iql_queues table.
queue_table	Name of the queue table that holds this queue. This name is used in the queue_phys_descr column of the iql_queues table. Note: Multiple queues can be stored in the same queue table.
retry_delay	Delay time, in seconds, before a message is scheduled for processing again after an application rollback.
max_retries	Number of times that a dequeue with the REMOVE mode can be attempted on a message. The count is incremented when the application issues a rollback after executing the dequeue. The message is moved to the default exception queue when it is reaches its max_retries.

The following example, from the init2Kora.sql script, shows the SQL used to create one of the default background Mbox queues that is created when the iProcess Engine is installed.

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DBMS_AQADM.CREATE_QUEUE (queue_name => 'TABLE_OWNER.bgmboxqueue1', queue_table => 'TABLE_OWNER.bgmboxtable1', retry_delay => 300, max_retries => 12);

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2.	Use the DBMS_AQADM.START_QUEUE procedure to start the queue.

3.	Use the DBMS_AQADM.GRANT_QUEUE_PRIVILEGE procedure to grant the privileges on the queue. The following parameters are required.

Column	Description
privilege	The AQ queue privilege to grant. This value must be ALL (which means both ENQUEUE and DEQUEUE).
queue_name	Name of the queue.
grantee	Grantee. This value must be the name of the iProcess Oracle Foreground user. Note: The Oracle Foreground user is defined in the third entry (after the second backslash character) on line 9 of the SWDIR\etc\staffpms file. For example: 3\swpro\swuser\swpro\staffdb1\10\0
grant_option	Defines whether the access privilege is granted with the GRANT option or not. This value must be false.

The following example, from the init2Kora.sql script, shows the SQL used to grant the required privileges on one of the default background Mbox queues that is created when the iProcess Engine is installed.

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dbms_aqadm.grant_queue_privilege (privilege => 'all', queue_name => 'TABLE_OWNER.bgmboxqueue1', grantee => 'FOREGROUND_USER', grant_option => false )

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Example

Suppose that the volume of messages handled by your system has increased significantly, and the default messages queues are no longer able to cope. To deal with the additional load you have decided that you need to add a new BGMBOX3 message queue to the BGMBSET Mboxset. This queue requires a new bgmboxqueue3 Oracle AQ queue and bgmboxtable3 queue table .

This example uses UNIX syntax.

To do this:

1.	Use SQLPLUS to connect to the Oracle instance.

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$ORACLE_HOME/bin/sqlplus

connect swpro/staffpro1;

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2.	Create an AQ queue table called bgmboxtable3.

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EXECUTE DBMS_AQADM.CREATE_QUEUE_TABLE (queue_table => 'swpro.bgmboxtable3', queue_payload_type => 'swpro.swlocalmsg', comment => '3rd background mbox', compatible => 8.1);

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3.	Create an AQ queue called bgmboxqueue3 in this queue table.

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EXECUTE DBMS_AQADM.CREATE_QUEUE (queue_name => 'swpro.bgmboxqueue3', queue_table => 'swpro.bgmboxtable3', retry_delay => 300, max_retries => 12);

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4.	Start the bgmboxqueue3 queue.

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EXECUTE DBMS_AQADM.START_QUEUE (queue_name => 'swpro.bgmboxqueue3');

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5.	Grant the required privileges on the bgmboxqueue3 queue.

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EXECUTE dbms_aqadm.grant_queue_privilege (privilege => 'all', queue_name => 'bgmboxqueue3', grantee => 'swuser', grant_option => false );

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6.	Commit the changes, disconnect and exit.

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commit;

disconnect;

exit;

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7.	Use the SWDIR\util\swadm utility to add a new message queue called BGMBOX3, which uses the bgmboxqueue3 queue.

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cd $SWDIR/util

swadm ADD_QUEUE BGMBOX3 Local 0001::bgmboxtable3:bgmboxqueue3

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8.	Add the BGMBOX3 queue to the BGMBSET Mbox set.

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swadm ADD_QUEUE_TO_MBOXSET 1 8

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1 is the number of the BGMBSET Mboxset (from the swadm SHOW_MBOXSETS command) and 8 is the number of the message queue (from the swadm SHOW_QUEUES command).

 

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