The MQUNSUBSCRIBE function is used to unregister an existing
message subscription. The subscriber-service, service-policy, and topic are used to identify the subscription that is to be cancelled.
Successful execution of this function causes the publish and subscribe
server to remove the specified subscription. Messages with the specified topic will no longer be sent to the logical destination
defined by subscriber-service. For more
details, visit http://www.ibm.com/software/MQSeries.
The data type of the result is VARCHAR(1). The result
of the function is '1' if successful or '0' if unsuccessful.
Syntax
>>-MQUNSUBSCRIBE------------------------------------------------>
>--(--+----------------------------------------------+--topic--)-><
'-subscriber-service--,--+-------------------+-'
'-service-policy--,-'
The schema is DB2MQ for non-transactional message
queuing functions, and DB2MQ1C for one-phase commit transactional
MQ functions.
Function parameters
- subscriber-service
- If specified, the subscriber-service must refer to a Subscribers Service Point defined in the DB2MQ.MQPUBSUB
table that has a type value of 'S' for publisher service. If subscriber-service is not specified, then the DB2.DEFAULT.SUBSCRIBER
will be used instead. The maximum size of subscriber-service is 48
bytes.
- service-policy
- If specified, the service-policy must
refer to a Policy defined in the DB2MQ.MQPOLICY table. A Service Policy
defines a set of quality of service options to be applied to this
messaging operation. If service-policy is
not specified, then the default DB2.DEFAULT.POLICY will be used. The maximum
size of service-policy is 48 bytes.
- topic
- A string specifying the subject of messages that are not to be
received. The maximum size of topic is 40
bytes. Multiple topics can be specified in one string (up to 40 bytes
long). Each topic must be separated by a colon. For example, "t1:t2:the
third topic" indicates that the message is associated with all three
topics: t1, t2, and "the third topic".
Authorization
One of the following authorities
is required to execute the function:
- EXECUTE privilege on the function
- DATAACCESS authority
- DBADM authority
- SQLADM authority
Examples
Example 1: This example cancels
an interest in messages containing the topic "Weather". The default
subscriber-service (DB2.DEFAULT.SUBSCRIBER) is registered as the unsubscriber and
the default service-policy (DB2.DEFAULT.POLICY) specifies the quality of
service.
VALUES MQUNSUBSCRIBE('Weather')
Example 2: This example demonstrates a subscriber canceling
an interest in messages containing "Stocks". The subscriber is registered
as "PORTFOLIO-UPDATES" with policy "BASIC-POLICY".
VALUES MQUNSUBSCRIBE('PORTFOLIO-UPDATES','BASIC-POLICY','Stocks')