3 Basic Components

Object Name (object_name)

Names database objects. This naming convention applies to queues, queue tables, and object types.

object_name := VARCHAR2
object_name := [schema_name.]name

Names for objects are specified by an optional schema name and a name. If the schema name is not specified, then the current schema is assumed. The name must follow the reserved character guidelines in Oracle Database SQL Reference. The schema name, agent name, and the object type name can each be up to 30 bytes long. However, queue names and queue table names can be a maximum of 24 bytes.

Type Name (type_name)

Defines queue types.

type_name := VARCHAR2
type_name := object_type | "RAW"

For details on creating object types refer to Oracle Database Concepts. The maximum number of attributes in the object type is limited to 900.

To store payload of type RAW, Oracle Streams AQ creates a queue table with a LOB column as the payload repository. The size of the payload is limited to 32K bytes of data. Because LOB columns are used for storing RAW payload, the Oracle Streams AQ administrator can choose the LOB tablespace and configure the LOB storage by constructing a LOB storage string in the storage_clause parameter during queue table creation time.

AQ Agent Type (aq$_agent)

Identifies a producer or a consumer of a message.

TYPE aq$_agent IS OBJECT (
   name            VARCHAR2(30), 
   address         VARCHAR2(1024),
   protocol        NUMBER)

All consumers that are added as subscribers to a multiconsumer queue must have unique values for the AQ$_AGENT parameters. You can add more subscribers by repeatedly using the DBMS_AQADM.ADD_SUBSCRIBER procedure up to a maximum of 1024 subscribers for a multiconsumer queue. Two subscribers cannot have the same values for the NAME, ADDRESS, and PROTOCOL attributes for the AQ$_AGENT type. At least one of the three attributes must be different for two subscribers.

name (VARCHAR2(30))

Name of a producer or consumer of a message. The name of the agent can be the name of an application or a name assigned by an application. A queue can itself be an agent, enqueuing or dequeuing from another queue. The name must follow the reserved character guidelines in Oracle Database SQL Reference.

address (VARCHAR2(1024))

A character field of up to 1024 bytes that is interpreted in the context of the protocol. If the protocol is 0 (default), then the address is of the form [schema.]queue[@dblink].

protocol (NUMBER)

Protocol to interpret the address and propagate the message. The default value is 0.

AQ Recipient List Type (aq$_recipient_list_t)

Identifies the list of agents that receive the message.

TYPE aq$_recipient_list_t IS TABLE OF aq$_agent
           INDEX BY BINARY_INTEGER; 

AQ Agent List Type (aq$_agent_list_t)

Identifies the list of agents for DBMS_AQ.LISTEN to listen for.

TYPE aq$_agent_list_t IS TABLE OF aq$_agent 
           INDEX BY BINARY INTEGER; 

AQ Subscriber List Type (aq$_subscriber_list_t)

Identifies the list of subscribers that subscribe to this queue.

TYPE aq$_subscriber_list_t IS TABLE OF aq$_agent
          INDEX BY BINARY INTEGER; 

AQ Registration Information List Type (aq$_reg_info_list)

Identifies the list of registrations to a queue.

TYPE aq$_reg_info_list AS VARRAY(1024) OF sys.aq$_reg_info

AQ Post Information List Type (aq$_post_info_list)

Identifies the list of anonymous subscriptions to which messages are posted.

TYPE aq$_post_info_list AS VARRAY(1024) OF sys.aq$_post_info

AQ Registration Information Type (aq$_reg_info)

The aq$_reg_info data structure identifies a producer or a consumer of a message.

TYPE sys.aq$_reg_info IS OBJECT (
   name      VARCHAR2(128),
   namespace NUMBER,
   callback  VARCHAR2(4000),
   context   RAW(2000));

name

Specifies the name of the subscription. The subscription name is of the form schema.queue if the registration is for a single consumer queue and schema.queue:consumer_name if the registration is for a multiconsumer queue.

namespace

Specifies the namespace of the subscription. To receive notifications from Oracle Streams AQ queues, the namespace must be DBMS_AQ.NAMESPACE_AQ. To receive notifications from other applications using DBMS_AQ.POST or OCISubscriptionPost(), the namespace must be DBMS_AQ.NAMESPACE_ANONYMOUS.

callback

Specifies the action to be performed on message notification. For e-mail notifications, the form is mailto://xyz@company.com. For Oracle Streams AQ PL/SQL Callback, use plsql://schema.procedure?PR=0 for raw message payload or plsql://schema.procedure?PR=1 for Oracle object type message payload converted to XML.

context

Specifies the context that is to be passed to the callback function. The default is NULL.

Table 3-1 shows the actions performed for nonpersistent queues for different notification mechanisms when RAW presentation is specified. Table 3-2 shows the actions performed when XML presentation is specified.

AQ Notification Descriptor Type

The aq$_descriptor data structure specifies the Oracle Streams AQ Descriptor received by the Oracle Streams AQ PL/SQL callbacks upon notification.

TYPE sys.aq$_descriptor IS OBJECT (
  queue_name    VARCHAR2(30),
  consumer_name VARCHAR2(30),
  msg_id        RAW(16),
  msg_prop      msg_prop_t);

queue_name

Name of the queue in which the message was enqueued which resulted in the notification.

consumer_name

Name of the consumer for the multiconsumer queue.

msg_id

ID of the message.

msg_prop

Message properties.

AQ Post Information Type

The aq$_post_info data structure specifies anonymous subscriptions to which you want to post messages.

TYPE sys.aq$_post_info IS OBJECT (
  name       VARCHAR2(128),
  namespace  NUMBER,
  payload    RAW(2000));

name

Name of the anonymous subscription to which you want to post.

namespace

To receive notifications from other applications using DBMS_AQ.POST or OCISubscriptionPost(), the namespace must be DBMS_AQ.NAMESPACE_ANONYMOUS.

payload

The payload to be posted to the anonymous subscription. The default is NULL.

Enumerated Constants in the Oracle Streams AQ Administrative Interface

When enumerated constants such as INFINITE, TRANSACTIONAL, and NORMAL_QUEUE are selected as values, the symbol must be specified with the scope of the packages defining it. All types associated with the administrative interfaces must be prepended with DBMS_AQADM. For example:

DBMS_AQADM.NORMAL_QUEUE

Table 3-3 lists the enumerated constants.

Enumerated Constants in the Oracle Streams AQ Operational Interface

When using enumerated constants such as BROWSE, LOCKED, and REMOVE, the PL/SQL constants must be specified with the scope of the packages defining them. All types associated with the operational interfaces must be prepended with DBMS_AQ. For example:

DBMS_AQ.BROWSE

Table 3-4 lists the enumerated constants.

INIT.ORA Parameter File Considerations

You can specify the AQ_TM_PROCESSES and JOB_QUEUE_PROCESSES parameters in the init.ora parameter file.

ALTER SYSTEM SET AQ_TM_PROCESSES=X