2 Basic Components

2.1 Object Name

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

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

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.

2.2 Type Name

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

This component defines queue types. 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 payloads 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.

2.3 AQ Agent Type

TYPE AQ$_AGENT IS OBJECT (
   name            VARCHAR2(30), 
   address         VARCHAR2(1024),
   protocol        NUMBER);

This component identifies a producer or a consumer of a message.

All consumers that are added as subscribers to a multiconsumer queue must have unique values for the AQ$_AGENT parameters. Two subscribers cannot have the same values for the NAME, ADDRESS, and PROTOCOL attributes for the AQ$_AGENT type. At least one of the three attributes must be different for two subscribers.

You can add subscribers by repeatedly using the DBMS_AQADM.ADD_SUBSCRIBER procedure up to a maximum of 1024 subscribers for a multiconsumer queue.

This type has three attributes:

• name

  This attribute specifies the name of a producer or consumer of a message. It 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

  This attribute is interpreted in the context of protocol. If protocol is 0 (default), then address is of the form [schema.]queue[@dblink].

• protocol

  This attribute specifies the protocol to interpret the address and propagate the message. The default value is 0.

2.4 AQ Recipient List Type

TYPE AQ$_RECIPIENT_LIST_T IS TABLE OF aq$_agent
           INDEX BY BINARY_INTEGER;
 

This component identifies the list of agents that receive a message.

2.5 AQ Agent List Type

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

This component identifies the list of agents for DBMS_AQ.LISTEN to listen for.

2.6 AQ Subscriber List Type

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

This component identifies the list of subscribers that subscribe to this queue.

2.7 AQ Registration Information List Type

TYPE AQ$_REG_INFO_LIST AS VARRAY(1024) OF sys.aq$_reg_info;

This component identifies the list of registrations to a queue.

2.8 AQ Post Information List Type

TYPE AQ$_POST_INFO_LIST AS VARRAY(1024) OF sys.aq$_post_info;

This component identifies the list of anonymous subscriptions to which messages are posted.

2.9 AQ Registration Information Type

TYPE SYS.AQ$_REG_INFO IS OBJECT (
   name           VARCHAR2(128),
   namespace      NUMBER,
   callback       VARCHAR2(4000),
   context        RAW(2000),
   qosflags       NUMBER,
   timeout        NUMBER);

This component identifies a producer or a consumer of a message. Its attributes are described in the following list. Attributes qosflags and timeout are part of Oracle Streams AQ 10g Release 2 (10.2) notification enhancements.

• name

  This attribute specifies the name of the subscription. If the registration is for a single-consumer queue, then it is of the form schema.queue. If the registration is for a multiconsumer queue, then it is of the form schema.queue:consumer_name.

• namespace

  This attribute 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

  This attribute 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

  This attribute specifies the context that is to be passed to the callback function. The default is NULL.

• qosflags

  This attribute specifies the notification quality of service, described in more detail in "Notification Quality of Service".

• timeout

  Clients can use this attribute to specify an automatic expiration period for the registration. If you want no timeout, then set this attribute to 0.

Notification Quality of Service

The qosflags attribute can be set to one or more of the following values to specify the notification quality of service:

• NTFN_QOS_RELIABLE

  This value specifies that reliable notification is required. Reliable notifications persist across instance and database restarts. The corresponding OCI flag is OCI_SUBSCR_QOS_RELIABLE.

• NTFN_QOS_PAYLOAD

  This value specifies that payload delivery is required. It is supported only for client notification and only for RAW queues. The corresponding OCI flag is OCI_SUBSCR_QOS_PAYLOAD.

• NTFN_QOS_PURGE_ON_NTFN

  This value specifies that the registration is to be purged automatically when the first notification is delivered to this registration location. The corresponding OCI flag is OCI_SUBSCR_QOS_PURGE_ON_NTFN.

2.10 AQ Notification Descriptor Type

TYPE SYS.AQ$_DESCRIPTOR IS OBJECT (
  queue_name    VARCHAR2(65),
  consumer_name VARCHAR2(30),
  msg_id        RAW(16),
  msg_prop      msg_prop_t,
  gen_desc      AQ$_NTFN_DESCRIPTOR);  

This component specifies the Oracle Streams AQ descriptor received by Oracle Streams AQ PL/SQL callbacks upon notification. It has the following attributes:

• queue_name

  This attribute specifies the name of the queue in which the message was enqueued which resulted in the notification.

• consumer_name

  This attribute specifies the name of the consumer for a multiconsumer queue.

• msg_id

  This attribute specifies the message identifier.

• msg_prop

  This attribute specifies the message properties.

• gen_desc

  This attribute indicates the timeout specifications

The message properties type msg_prop_t has the following components:

TYPE AQ$_MSG_PROP_T IS OBJECT(
   priority         number,
   delay            number,
   expiration       number,
   correlation      varchar2(128),
   attempts         number,
   recipent_list    aq$_recipient_list_t,
   exception_queue  varchar2(51),
   enqueue_time     date,
   state            number,
   sender_id        aq$_agent,
   original_misgid  raw(16),
   delivery_mode    number);

The timeout specifications type AQ$_NTFN_DESCRIPTOR has a single component:

TYPE AQ$_NTFN_DESCRIPTOR IS OBJECT(
   NTFN_FLAGS   number);

NTFN_FLAGS is set to 1 if the notifications are already removed after a stipulated timeout; otherwise the value is 0.

2.11 AQ Post Information Type

TYPE SYS.AQ$_POST_INFO IS OBJECT (
  name       VARCHAR2(128),
  namespace  NUMBER,
  payload    RAW(2000));

This component specifies anonymous subscriptions to which you want to post messages. It has three attributes:

• name

  This attribute specifies the name of the anonymous subscription to which you want to post.

• namespace

  This attribute specifies the namespace of the anonymous subscription. To receive notifications from other applications using DBMS_AQ.POST or OCISubscriptionPost(), the namespace must be DBMS_AQ.NAMESPACE_ANONYMOUS.

• payload

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

2.12 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 2-1 lists the enumerated constants in the Oracle Streams AQ administrative interface.

2.13 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 2-2 lists the enumerated constants in the Oracle Streams AQ operational interface.

2.14 INIT.ORA Parameter File Considerations

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

ALTER SYSTEM SET AQ_TM_PROCESSES=X