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TD_READ
If a queue is defined as logically recoverable, a TD_READ wait may be encountered. A task can read from a queue while another task is writing to the same queue. If this happens, the first task holds the read enqueue and the second task holds the write enqueue on the queue. The task reading the queue can only read data that has already been committed. It cannot read data that is currently being written to the queue until the task holding the write enqueue commits the changes it has made and dequeues from the write end of the queue.
A task is suspended on a resource type of TD_READ if it is trying to read uncommitted data from a logically recoverable queue. The queue name is displayed in a qualifier. The suspended task is forced to wait until the task owning the write enqueue commits the changes it has made.
In most cases, the suspended task will not have to wait long. A lengthy wait can occur if the task owning the write enqueue suffers from an indoubt failure (which causes the associated UOW to be shunted), and the queue is defined with the WAIT=YES and WAITACTION=QUEUE attributes.
If you do not want to wait for data to be committed to the queue, code NOSUSPEND on the READQ TD request. QBUSY is returned to the application and the task does not wait.