In-flight Work Associated with Producers
The following types of messages are inserted on a destination as a result of in-flight work associated with message producers.
- Unborn Messages - Messages that are created by the producer with "birth time" (TimeToDeliver) set in the future. Until delivered, unborn messages are counted as "pending" messages in the destination statistics and are not available for consumption.
- Uncommitted Messages - Messages that are produced as part of a transaction (using either user transaction or transacted session) and have not yet been either committed or rolled back. Until the transaction has been completed, uncommitted messages are counted as "pending" messages in the destination statistics and are not available for consumption.
- Quota Blocking Send - Messages that, if initially prevented from reaching a destination due to a quota limit, will block for a specific period of time while waiting for the destination to become available. The message may exceed the message quota limit, the byte quota limit, or both quota limits on the destination. While blocking, these messages are invisible to the system and are not counted against any of the destination statistics.
In-flight Work Associated with Consumers
The following types of messages are inserted on a destination as a result of in-flight work associated with message consumers.
- Unacknowledged (CLIENT ACK PENDING) Messages - Messages that have been received by a client and are awaiting acknowledgement from the client. These are "pending messages" which are removed from the destination/system when the acknowledgement is received.
- Uncommitted Messages - Messages that have been received by a client within a transaction which has not yet been committed or rolled back. When the client successfully commits the transaction the messages are removed from the system.
- Rolled-back Messages - Messages that are put back on a destination because of the successful rollback of a transaction.
These messages might or might not be ready for redelivery to the clients immediately, depending on the redelivery parameters (i.e., RedeliveryDelay and/or RedeliveryDelayOverride and RedeliveryLimit) configured on the associated connection factory and destination.
If there is a redelivery delay configured, then, for the duration of that delay, the messages are not available for redelivery and the messages are counted as "pending" in the destination statistics. After the delay period, if the redelivery limit has not been exceeded, then they are delivered and are counted as "current" messages in the destination statistics. If the redelivery limit has been exceeded, then the messages are moved to the error destination, if one has been configured, or are dropped, if no error destination has been configured.
- Recovered Messages - Messages that appear on the queue because of an explicit call to session "recover" by the client. These messages are similar to the Rolled-back Messages discussed above.
Redelivered Messages - Messages that reappear on the destination because of an unsuccessful delivery attempt to the client. These messages are similar to the Rolled-back Messages discussed above.
