271 Oracle Database Advanced Queuing (AQ) Types

This chapter describes the types used with Oracle Database Advanced Queuing (AQ) packages for PL/SQL, DBMS_AQ, and DBMS_AQADM.

See Also:

Oracle Database Advanced Queuing User's Guide for information about using Oracle Database Advanced Queuing.

This chapter contains the following topics:

Using Oracle Database Advanced Queuing Types

This section contains the following topic:

Security Model

PUBLIC is granted EXECUTE privilege on the types described in this chapter.

Summary of Types

AQ$_AGENT Type

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

Syntax

TYPE SYS.AQ$_AGENT IS OBJECT (
   name       VARCHAR2(30),
   address    VARCHAR2(1024),
   protocol   NUMBER  DEFAULT 0);

Attributes

Table 271-1 AQ$_AGENT Attributes

Attribute Description

name

Name of a producer or consumer of a message. The name must follow object name guidelines in the Oracle Database SQL Language Reference with regard to reserved characters.

address

Protocol-specific address of the recipient. If the protocol is 0, then the address is of the form [schema.]queue[@dblink].

For example, a queue named emp_messages in the HR queue at the site dbs1.net has the address: hr.emp_messages@dbs1.net

protocol

Protocol to interpret the address and propagate the message. Protocols 1-127 are reserved for internal use. If the protocol number is in the range 128 - 255, the address of the recipient is not interpreted by Oracle Database Advanced Queuing.

AQ$_AGENT_LIST_T Type

This type identifies the list of agents for which DBMS_AQ.LISTEN listens.

See Also:

"AQ$_AGENT Type"

Syntax

TYPE SYS.AQ$_AGENT_LIST_T IS TABLE OF SYS.AQ$_AGENT 
   INDEX BY BINARY INTEGER;

AQ$_DESCRIPTOR Type

This type specifies the Oracle Database Advanced Queuing descriptor received by the AQ PL/SQL callbacks upon notification.

See Also:

"MESSAGE_PROPERTIES_T Type"

Syntax

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);

Attributes

Table 271-2 AQ$_DESCRIPTOR Attributes

Attribute Description

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

Identification number of the message

msg_prop

Message properties specified by the MSG_PROP_T type

gen_desc

Indicates the timeout specifications

msgid_array

Group notification message ID list

ntfnsRecdInGrp

Notifications received in group

AQ$_NTFN_DESCRIPTOR Type

This type is for storing a generic notification descriptor regarding PL/SQL notification flags.

Syntax

TYPE SYS.AQ$_NTFN_DESCRIPTOR IS OBJECT(   ntfn_flags   NUMBER)

Attributes

Table 271-3 AQ$_NTFN_DESCRIPTOR Attributes

Attribute Description

ntfn_flags

Set to 1 if the notifications are already removed after a stipulated timeout. Set 2 to denote grouping. Default is 0.

AQ$_NTFN_MSGID_ARRAY Type

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

Syntax

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

AQ$_POST_INFO Type

Specifies anonymous subscriptions to which you want to post messages.

Syntax

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

Attributes

Table 271-4 AQ$_POST_INFO Attributes

Attribute Description

name

Name of the anonymous subscription to which you want to post

namespace

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

payload

The payload to be posted to the anonymous subscription

AQ$_POST_INFO_LIST Type

Identifies the list of anonymous subscriptions to which you want to post messages.

See Also:

AQ$_POST_INFO Type

Syntax

TYPE SYS.AQ$_POST_INFO_LIST AS VARRAY(1024) OF SYS.AQ$_POST_INFO;

AQ$_PURGE_OPTIONS_T Type

This type specifies the options available for purging a queue table.

See Also:

PURGE_QUEUE_TABLE Procedure.

Syntax

TYPE AQ$_PURGE_OPTIONS_T is RECORD (
   block           BOOLEAN       DEFAULT FALSE
   delivery_mode   PLS_INTEGER   DEFAULT PERSISTENT);

Table 271-5 AQ$_PURGE_OPTIONS_T Type Attributes

Attribute Description

block

TRUE/FALSE.

  • If block is TRUE, then an exclusive lock on all the queues in the queue table is held while purging the queue table. This will cause concurrent enqueuers and dequeuers to block while the queue table is purged. The purge call always succeeds if block is TRUE.

  • The default for block is FALSE. This will not block enqueuers and dequeuers, but it can cause the purge to fail with an error during high concurrency times.

delivery_mode

Kind of messages to purge, either DBMS_AQ.BUFFERED or DBMS_AQ.PERSISTENT

AQ$_RECIPIENT_LIST_T Type

Identifies the list of agents that receive the message. This type can be used only when the queue is enabled for multiple dequeues.

See Also:

"AQ$_AGENT Type"

Syntax

TYPE SYS.AQ$_RECIPIENT_LIST_T IS TABLE OF SYS.AQ$_AGENT
   INDEX BY BINARY_INTEGER;

AQ$_REG_INFO Type

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

Syntax

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);

Attributes

Table 271-6 AQ$_REG_INFO Type Attributes

Attribute Description

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 or schema.queue:consumer_name if the registration is for a multiconsumer queues.

namespace

Specifies the namespace of the subscription. To receive notification from Oracle Database Advanced Queuing queues, the namespace must be DBMS_AQ.NAMESPACE_AQ. To receive notifications from other applications through DBMS_AQ.POST or OCISubscriptionPost(), the namespace must be DBMS_AQ.NAMESPACE_ANONYMOUS.

callback

Specifies the action to be performed on message notification. For HTTP notifications, use http://www.company.com:8080. For e-mail notifications, use mailto://xyz@company.com. For raw message payload for the PLSQLCALLBACK procedure, use plsql://schema.procedure?PR=0. For user-defined type message payload converted to XML for the PLSQLCALLBACK procedure, use plsql://schema.procedure?PR=1

context

Specifies the context that is to be passed to the callback function

qosflags

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.

  • NTFN_QOS_PAYLOAD - This value specifies that payload delivery is required. It is supported only for client notification and only for RAW queues.

  • 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.

ntfn_grouping_class

Currently, only the following flag can be set to specify criterion for grouping. The default value will be 0. If ntfn_grouping_class is 0, all other notification grouping attributes must be 0.

  • NTFN_GROUPING_CLASS_TIME - Notifications grouped by time, that is, the user specifies a time value and a single notification gets published at the end of that time.

ntfn_grouping_value

Time-period of grouping notifications specified in seconds, meaning the time after which grouping notification would be sent periodically until ntfn_grouping_repeat_count is exhausted.

ntfn_grouping_type

  • NTFN_GROUPING_TYPE_SUMMARY - Summary of all notifications that occurred in the time interval. (Default)

  • NTFN_GROUPING_TYPE_LAST - Last notification that occurred in the interval.

ntfn_grouping_start_time

Notification grouping start time. Notification grouping can start from a user-specified time that should a valid timestamp with time zone. If ntfn_grouping_start_time is not specified when using grouping, the default is to current timestamp with time zone

ntfn_grouping_repeat_count

Grouping notifications will be sent as many times as specified by the notification grouping repeat count and after that revert to regular notifications. The ntfn_grouping_repeat_count, if not specified, will default to

  • NTFN_GROUPING_FOREVER - Keep sending grouping notifications forever.

Usage Notes

You can use the following notification mechanisms:

  • OCI callback

  • e-mail callback

  • PL/SQL callback

Table 271-7 shows the actions performed for nonpersistent queues for different notification mechanisms when RAW presentation is specified. Table 271-8 shows the actions performed when XML presentation is specified.

Table 271-7 Actions Performed for Nonpersistent Queues When RAW Presentation Specified

Queue Payload Type OCI Callback E-mail PL/SQL Callback

RAW

OCI callback receives the RAW data in the payload.

Not supported

PL/SQL callback receives the RAW data in the payload.

Oracle object type

Not supported

Not supported

Not supported

Table 271-8 Actions Performed for Nonpersistent Queues When XML Presentation Specified

Queue Payload Type OCI Callback E-mail PL/SQL Callback

RAW

OCI callback receives the XML data in the payload.

XML data is formatted as a SOAP message and e-mailed to the registered e-mail address.

PL/SQL callback receives the XML data in the payload.

Oracle object type

OCI callback receives the XML data in the payload.

XML data is formatted as a SOAP message and e-mailed to the registered e-mail address.

PL/SQL callback receives the XML data in the payload.

AQ$_REG_INFO_LIST Type

Identifies the list of registrations to a queue.

See Also:

"AQ$_REG_INFO Type"

Syntax

TYPE SYS.AQ$_REG_INFO_LIST AS VARRAY(1024) OF SYS.AQ$_REG_INFO;

AQ$_SUBSCRIBER_LIST_T Type

Identifies the list of subscribers that subscribe to a queue.

See Also:

"AQ$_AGENT Type"

Syntax

TYPE SYS.AQ$_SUBSCRIBER_LIST_T IS TABLE OF SYS.AQ$_AGENT
   INDEX BY BINARY_INTEGER;

DEQUEUE_OPTIONS_T Type

Specifies the options available for the dequeue operation.

Syntax

TYPE DEQUEUE_OPTIONS_T IS RECORD (
   consumer_name     VARCHAR2(30)    DEFAULT NULL,
   dequeue_mode      BINARY_INTEGER  DEFAULT REMOVE,
   navigation        BINARY_INTEGER  DEFAULT NEXT_MESSAGE,
   visibility        BINARY_INTEGER  DEFAULT ON_COMMIT,
   wait              BINARY_INTEGER  DEFAULT FOREVER,
   msgid             RAW(16)         DEFAULT NULL,
   correlation       VARCHAR2(128)   DEFAULT NULL,
   deq_condition     VARCHAR2(4000)  DEFAULT NULL,
   signature         aq$_sig_prop    DEFAULT NULL,
   transformation    VARCHAR2(61)    DEFAULT NULL,
   delivery_mode     PLS_INTEGER     DEFAULT PERSISTENT);

Attributes

Table 271-9 DEQUEUE_OPTIONS_T Attributes

Attribute Description

consumer_name

Name of the consumer. Only those messages matching the consumer name are accessed. If a queue is not set up for multiple consumers, then this field should be set to NULL.

For secure queues, consumer_name must be a valid AQ agent name, mapped to the database user performing the dequeue operation, through dbms_aqadm.enable_db_access procedure call.

dequeue_mode

Specifies the locking behavior associated with the dequeue. Possible settings are:

BROWSE: Read the message without acquiring any lock on the message. This specification is equivalent to a select statement.

LOCKED: Read and obtain a write lock on the message. The lock lasts for the duration of the transaction. This setting is equivalent to a select for update statement.

REMOVE: Read the message and delete it. This setting is the default. The message can be retained in the queue table based on the retention properties.

REMOVE_NODATA: Mark the message as updated or deleted. The message can be retained in the queue table based on the retention properties.

navigation

Specifies the position of the message that will be retrieved. First, the position is determined. Second, the search criterion is applied. Finally, the message is retrieved. Possible settings are:

NEXT_MESSAGE: Retrieve the next message that is available and matches the search criteria. If the previous message belongs to a message group, then AQ retrieves the next available message that matches the search criteria and belongs to the message group. This setting is the default.

NEXT_TRANSACTION: Skip the remainder of the current transaction group (if any) and retrieve the first message of the next transaction group. This setting can only be used if message grouping is enabled for the current queue.

FIRST_MESSAGE: Retrieves the first message which is available and matches the search criteria. This setting resets the position to the beginning of the queue.

FIRST_MESSAGE_MULTI_GROUP: indicates that a call to DBMS_AQ.DEQUEUE_ARRAY will reset the position to the beginning of the queue and dequeue messages (possibly across different transaction groups) that are available and match the search criteria, until reaching the ARRAY_SIZE limit. Refer to the TRANSACTION_GROUP attribute for the message to distinguish between transaction groups.

NEXT_MESSAGE_MULTI_GROUP: indicates that a call to DBMS_AQ.DEQUEUE_ARRAY will dequeue the next set of messages (possibly across different transaction groups) that are available and match the search criteria, until reaching the ARRAY_SIZE limit. Refer to the TRANSACTION_GROUP attribute for the message to distinguish between transaction groups.

visibility

Specifies whether the new message is dequeued as part of the current transaction.The visibility parameter is ignored when using the BROWSE dequeue mode. Possible settings are:

ON_COMMIT: The dequeue will be part of the current transaction. This setting is the default.

IMMEDIATE: The dequeue operation is not part of the current transaction, but an autonomous transaction which commits at the end of the operation.

wait

Specifies the wait time if there is currently no message available which matches the search criteria. Possible settings are:

FOREVER: Wait forever. This setting is the default.

NO_WAIT: Do not wait.

number: Wait time in seconds.

msgid

Specifies the message identifier of the message to be dequeued.

correlation

Specifies the correlation identifier of the message to be dequeued. Special pattern matching characters, such as the percent sign (%) and the underscore (_) can be used. If more than one message satisfies the pattern, then the order of dequeuing is undetermined.

deq_condition

A conditional expression based on the message properties, the message data properties, and PL/SQL functions.

A deq_condition is specified as a Boolean expression using syntax similar to the WHERE clause of a SQL query. This Boolean expression can include conditions on message properties, user data properties (object payloads only), and PL/SQL or SQL functions (as specified in the WHERE clause of a SQL query). Message properties include priority, corrid and other columns in the queue table

To specify dequeue conditions on a message payload (object payload), use attributes of the object type in clauses. You must prefix each attribute with tab.user_data as a qualifier to indicate the specific column of the queue table that stores the payload. The deq_condition parameter cannot exceed 4000 characters. If more than one message satisfies the dequeue condition, then the order of dequeuing is undetermined.

signature

Currently not implemented

transformation

Specifies a transformation that will be applied after dequeuing the message. The source type of the transformation must match the type of the queue.

delivery_mode

The dequeuer specifies the delivery mode of the messages it wishes to dequeue in the dequeue options. It can be BUFFERED or PERSISTENT or PERSISTENT_OR_BUFFERED. The message properties of the dequeued message indicate the delivery mode of the dequeued message. Array dequeue is only supported for buffered messages with an array size of '1'.

ENQUEUE_OPTIONS_T Type

Specifies the options available for the enqueue operation.

Syntax

TYPE SYS.ENQUEUE_OPTIONS_T IS RECORD (
   visibility            BINARY_INTEGER  DEFAULT ON_COMMIT,
   relative_msgid        RAW(16)         DEFAULT NULL,
   sequence_deviation    BINARY_INTEGER  DEFAULT NULL,
   transformation        VARCHAR2(61)    DEFAULT NULL,
   delivery_mode         PLS_INTEGER     NOT NULL DEFAULT PERSISTENT);

Attributes

Table 271-10 ENQUEUE_OPTIONS_T Attributes

Attribute Description

visibility

Specifies the transactional behavior of the enqueue request. Possible settings are:

ON_COMMIT: The enqueue is part of the current transaction. The operation is complete when the transaction commits. This setting is the default.

IMMEDIATE: The enqueue operation is not part of the current transaction, but an autonomous transaction which commits at the end of the operation. This is the only value allowed when enqueuing to a non-persistent queue.

relative_msgid

Specifies the message identifier of the message which is referenced in the sequence deviation operation. This field is valid only if BEFORE is specified in sequence_deviation. This parameter is ignored if sequence deviation is not specified.

sequence_deviation

Specifies whether the message being enqueued should be dequeued before other messages already in the queue. Possible settings are:

BEFORE: The message is enqueued ahead of the message specified by relative_msgid.

TOP: The message is enqueued ahead of any other messages.

transformation

Specifies a transformation that will be applied before enqueuing the message. The return type of the transformation function must match the type of the queue.

delivery_mode

The enqueuer specifies the delivery mode of the messages it wishes to enqueue in the enqueue options. It can be BUFFERED or PERSISTENT. The message properties of the enqueued message indicate the delivery mode of the enqueued message. Array enqueue is only supported for buffered messages with an array size of '1'.

SYS.MSG_PROP_T Type

This type is used in PL/SQL notification, as one field in aq$_descriptor, to pass message properties of an AQ message to the PL/SQL notification client callback.

Syntax

CREATE or replace TYPE sys.msg_prop_t AS OBJECT (
   priority         NUMBER,
   delay            NUMBER,
   expiration       NUMBER,
   correlation      VARCHAR2(128),
   attempts         NUMBER,
   exception_queue  VARCHAR2(51),
   enqueue_time     DATE,
   state            NUMBER,
   sender_id        aq$_agent,
   original_msgid   RAW(16),
   delivery_mode    NUMBER);

Parameters

Table 271-11 SYS.MSG_PROP_T Type Attributes

Parameter Description

priority

Specifies the priority of the message. A smaller number indicates higher priority. The priority can be any number, including negative numbers.

delay

Specifies the delay of the enqueued message. The delay represents the number of seconds after which a message is available for dequeuing. Dequeuing by msgid overrides the delay specification. A message enqueued with delay set is in the WAITING state, and when the delay expires, the message goes to the READY state. DELAY processing requires the queue monitor to be started. However the queue monitor is started automatically by the system if needed. Delay is set by the producer who enqueues the message.

The possible settings follow:

NO_DELAY: The message is available for immediate dequeuing

number: The number of seconds to delay the message

expiration

Specifies the expiration of the message. It determines, in seconds, the duration the message is available for dequeuing. This parameter is an offset from the time the message is ready for dequeue. Expiration processing requires the queue monitor to be running. However the queue monitor is started automatically by the system if needed.

The possible settings follow:

NEVER: The message does not expire

number: The number of seconds message remains in READY state. If the message is not dequeued before it expires, then it is moved to the exception queue in the EXPIRED state.

correlation

Returns the identifier supplied by the producer of the message at enqueue time.

attempts

Returns the number of attempts that have been made to dequeue the message. This parameter cannot be set at enqueue time.

exception_queue

Specifies the name of the queue into which the message is moved if it cannot be processed successfully.

Messages are moved automatically into the exception queue. Messages are moved into the exception queue in the following cases:

  • RETRY_COUNT, the number of unsuccessful dequeue attempts, has exceeded the specification for the MAX_RETRIES parameter in the DBMS_AQADM.CREATE_QUEUE procedure during queue creation.

    For multiconsumer queues, the message becomes eligible to be moved to the exception queue even if failed dequeue attempts exceeds the MAX_RETRIES parameter for only one of the consumers. But the message will not be moved until either all other consumers have successfully consumed the message or failed more than MAX_RETRIES. You can view MAX_RETRIES for a queue in the ALL_QUEUES data dictionary view.

    If a dequeue transaction fails because the server process dies (including ALTER SYSTEM KILL SESSION) or SHUTDOWN ABORT on the instance, then RETRY_COUNT is not incremented.

  • A message was not dequeued before the expiration time elapsed.

  • Message propagation to the specified destination queue failed with one of the following errors:

    * There were no recipients for the multiconsumer destination queue.

    * Recipients were specified for a single-consumer destination queue.

    * Destination queue was an exception queue

    * There was an error when applying transformation.

The default is the exception queue associated with the queue table. If the exception queue specified does not exist at the time of the move, then the message is moved to the default exception queue associated with the queue table, and a warning is logged in the alert log. If the default exception queue is specified, then the parameter returns a NULL value at dequeue time.

enqueue_time

Specifies the time the message was enqueued. This value is determined by the system and cannot be set by the user at enqueue time.

state

Specifies the state of the message at the time of the dequeue. This parameter cannot be set at enqueue time. The possible states follow:

  • DBMS_AQ.READY: The message is ready to be processed.

  • DBMS_AQ.WAITING: The message delay has not yet been reached.

  • DBMS_AQ.PROCESSED: The message has been processed and is retained.

  • DBMSAQ.EXPIRED: The message has been moved to the exception queue.

sender_id

The application-sender identification specified at enqueue time by the message producer. Sender id is of type aq$_agent.

Sender name is required for secure queues at enqueue time. This must be a valid AQ agent name, mapped to the database user performing the enqueue operation, through dbms_aqadm.enable_db_access procedure call. Sender address and protocol should not be specified.

The Sender id in the message properties returned at dequeue time may have a sender address if the message was propagated from another queue. The value of the address is the source_queue, source database name if it was a remote database [format source_queue@source_database_name]

original_msgid

This parameter is used by Oracle Database Advanced Queuing for propagating messages.

delivery_mode

DBMS_AQ.BUFFERED or DBMS_AQ.PERSISTENT.

MESSAGE_PROPERTIES_T Type

This type is defined inside the DBMS_AQ package, and describes the information that AQ uses to convey the state of individual messages. These are set at enqueue time, and their values are returned at dequeue time.

See Also:

AQ$_RECIPIENT_LIST_T Type

Syntax

TYPE message_properties_t IS RECORD (
   priority               BINARY_INTEGER  NOT NULL DEFAULT 1,
   delay                  BINARY_INTEGER  NOT NULL DEFAULT NO_DELAY,
   expiration             BINARY_INTEGER  NOT NULL DEFAULT NEVER,
   correlation            VARCHAR2(128)   DEFAULT NULL,
   attempts               BINARY_INTEGER,
   recipient_list         AQ$_RECIPIENT_LIST_T,
   exception_queue        VARCHAR2(61)    DEFAULT NULL,
   enqueue_time           DATE,
   state                  BINARY_INTEGER,
   sender_id              SYS.AQ$_AGENT   DEFAULT NULL, 
   original_msgid         RAW(16)         DEFAULT NULL,
   signature              aq$_sig_prop    DEFAULT NULL,
   transaction_group      VARCHAR2(30)    DEFAULT NULL,
   user_property          SYS.ANYDATA     DEFAULT NULL
   delivery_mode          PLS_INTEGER     NOT NULL DEFAULT DBMS_AQ.PERSISTENT);

Attributes

Table 271-12 MESSAGE_PROPERTIES_T Attributes

Attribute Description

priority

Specifies the priority of the message. A smaller number indicates higher priority. The priority can be any number, including negative numbers.

delay

Specifies the delay of the enqueued message. The delay represents the number of seconds after which a message is available for dequeuing. Dequeuing by msgid overrides the delay specification. A message enqueued with delay set is in the WAITING state, and when the delay expires, the message goes to the READY state. DELAY processing requires the queue monitor to be started. However the queue monitor is started automatically by the system if needed. Delay is set by the producer who enqueues the message.

The possible settings follow:

NO_DELAY: The message is available for immediate dequeuing

number: The number of seconds to delay the message

expiration

Specifies the expiration of the message. It determines, in seconds, the duration the message is available for dequeuing. This parameter is an offset from the time the message is ready for dequeue. Expiration processing requires the queue monitor to be running. However the queue monitor is started automatically by the system if needed.

The possible settings follow:

NEVER: The message does not expire

number: The number of seconds message remains in READY state. If the message is not dequeued before it expires, then it is moved to the exception queue in the EXPIRED state.

correlation

Returns the identifier supplied by the producer of the message at enqueue time.

attempts

Returns the number of attempts that have been made to dequeue the message. This parameter cannot be set at enqueue time.

recipient_list

This parameter is only valid for queues that allow multiple consumers. The default recipients are the queue subscribers. This parameter is not returned to a consumer at dequeue time.

For type definition, see the "AQ$_AGENT Type".

exception_queue

Specifies the name of the queue into which the message is moved if it cannot be processed successfully.

Messages are moved automatically into the exception queue. Messages are moved into the exception queue in the following cases:

  • RETRY_COUNT, the number of unsuccessful dequeue attempts, has exceeded the specification for the MAX_RETRIES parameter in the DBMS_AQADM.CREATE_QUEUE procedure during queue creation.

    For multiconsumer queues, the message becomes eligible to be moved to the exception queue even if failed dequeue attempts exceeds the MAX_RETRIES parameter for only one of the consumers. But the message will not be moved until either all other consumers have successfully consumed the message or failed more than MAX_RETRIES. You can view MAX_RETRIES for a queue in the ALL_QUEUES data dictionary view.

    If a dequeue transaction fails because the server process dies (including ALTER SYSTEM KILL SESSION) or SHUTDOWN ABORT on the instance, then RETRY_COUNT is not incremented.

  • A message was not dequeued before the expiration time elapsed.

  • Message propagation to the specified destination queue failed with one of the following errors:

    * There were no recipients for the multiconsumer destination queue.

    * Recipients were specified for a single-consumer destination queue.

    * Destination queue was an exception queue

    * There was an error when applying transformation.

The default is the exception queue associated with the queue table. If the exception queue specified does not exist at the time of the move, then the message is moved to the default exception queue associated with the queue table, and a warning is logged in the alert log. If the default exception queue is specified, then the parameter returns a NULL value at dequeue time.

enqueue_time

Specifies the time the message was enqueued. This value is determined by the system and cannot be set by the user at enqueue time.

state

Specifies the state of the message at the time of the dequeue. This parameter cannot be set at enqueue time. The possible states follow:

  • DBMS_AQ.READY: The message is ready to be processed.

  • DBMS_AQ.WAITING: The message delay has not yet been reached.

  • DBMS_AQ.PROCESSED: The message has been processed and is retained.

  • DBMSAQ.EXPIRED: The message has been moved to the exception queue.

sender_id

The application-sender identification specified at enqueue time by the message producer. Sender id is of type aq$_agent.

Sender name is required for secure queues at enqueue time. This must be a valid AQ agent name, mapped to the database user performing the enqueue operation, through dbms_aqadm.enable_db_access procedure call. Sender address and protocol should not be specified.

The Sender id in the message properties returned at dequeue time may have a sender address if the message was propagated from another queue. The value of the address is the source_queue, source database name if it was a remote database [format source_queue@source_database_name]

original_msgid

This parameter is used by Oracle Database Advanced Queuing for propagating messages.

signature

Currently not implemented

transaction_group

Specifies the transaction_group for the dequeued message. Messages belonging to the same transaction group will have the same value for this attribute. This attribute is only set by the DBMS_AQ.DEQUEUE_ARRAY. This attribute cannot be used to set the transaction group of a message through DBMS_AQ.ENQUEUE or DBMS_AQ.ENQUEUE_ARRAY calls.

user_property

This optional attribute is used to store additional information about the payload.

delivery_mode

The message publisher specifies the delivery mode in the message_properties. This can be DBMS_AQ.BUFFERED or DBMS_AQ.PERSISTENT. Array enqueue is only supported for buffered messages with an array size of '1'.

MESSAGE_PROPERTIES_ARRAY_T Type

This type is used by dbms_aq.enqueue_array and dbms_aq.dequeue_array calls to hold the set of message properties. Each element in the payload_array should have a corresponding element in the MESSAGE_PROPERTIES_ARRAY_T VARRAY.

See Also:

"MESSAGE_PROPERTIES_T Type"

Syntax

TYPE MESSAGE_PROPERTIES_ARRAY_T IS VARRAY (2147483647)
   OF MESSAGE_PROPERTIES_T;

MSGID_ARRAY_T Type

The msgid_array_t type is used in dbms_aq.enqueue_array and dbms_aq.dequeue_array calls to hold the set of message IDs that correspond to the enqueued or dequeued messages.

Syntax

TYPE MSGID_ARRAY_T IS TABLE OF RAW(16) INDEX BY BINARY_INTEGER