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 Language 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 Language 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)  DEFAULT NULL,
   qosflags                          NUMBER,
   timeout                           NUMBER
   ntfn_grouping_class               NUMBER,
   ntfn_grouping_value               NUMBER    DEFAULT 600,
   ntfn_grouping_type                NUMBER,
   ntfn_grouping_start_time          TIMESTAMP WITH TIME ZONE,
   ntfn_grouping_repeat_count   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.

2.10 AQ Notification Descriptor Type

TYPE SYS.AQ$_DESCRIPTOR IS OBJECT (
   queue_name      VARCHAR2(61),
   consumer_name   VARCHAR2(30),
   msg_id          RAW(16),
   msg_prop        MSG_PROP_T,
   gen_desc        AQ$_NTFN_DESCRIPTOR,
   msgid_array     SYS.AQ$_NTFN_MSGID_ARRAY, 
   ntfnsRecdInGrp  NUMBER);

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

2.11 AQ Message Properties Type

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.

2.12 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.

2.13 AQ$_NTFN_MSGID_ARRAY Type

TYPE SYS.AQ$_NTFN_MSGID_ARRAY   AS VARRAY(1073741824)OF RAW(16);

This component is for storing grouping notification data for AQ namespace, value 2³⁰ which is the max varray size.

2.14 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 2-3 lists the enumerated constants in the Oracle Streams AQ administrative interface.

2.15 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 2-4 lists the enumerated constants in the Oracle Streams AQ operational interface.

2.16 AQ Background Processes

• Queue Monitor Processes

• Job Queue Processes