Sequence Number

Each message has a message sequence number that is assigned by the JMS IQ Manager when the message is added to the queue or topic. The message sequence number provides a message index, represented as a long integer value, and is unique across a topic or queue. For a transaction session, the message sequence number is determined by the JMS IQ Manager when a message is committed. For a non-transaction session, the message sequence number is determined by the JMS IQ Manager when the JMS IQ Manager receives the message.

The minimum sequence number of a topic or queue is the sequence number of the first unconsumed message in the topic or queue. The maximum sequence number of a topic or a queue is the sequence number of the last unconsumed message in the topic or queue. Because all messages in the topic or the queue are sorted and indexed by sequence number, the first unconsumed message has the minimum sequence number, and the last unconsumed message has the maximum sequence number, among those residing in the topic or queue. If no unconsumed message exists in the topic or queue, the minimum sequence number and the maximum sequence number are identical and represent the next available sequence number. This number will be assigned to the next message received by the topic or queue.

The following example displays the current status of the queue PTP:

stcmsctrlutil -host localhost -port 24055 -queuestat PTP
Queue Name: PTP
First enqueue time: 03212005:08:33:09
Last enqueue time: 03212005:08:33:10
Number of current receivers: 2
Message count: 4
Messages sent and committed: 245
Min sequence number: 245
Max sequence number: 248
Suspended: No

In this example, four messages are in the queue PTP. The minimum sequence number is the sequence number of the first message, which is 245, and the maximum sequence number is the sequence number of the fourth message, which is 248. If all four currently resident messages are consumed, both the minimum and maximum sequence numbers will represent the next available sequence number, which is 249. This number will be assigned to the next incoming message.

In the initial state, where the JMS IQ Manager has not received or consumed any messages in the topic or queue, both the minimum and maximum sequence numbers are 0 (zero).