Using Data Queue APIs

The advantages of using data queues are:

• Using data queues frees a job from performing some work. If the job is an interactive job, the data queue APIs can provide better response time and decrease the size of the interactive program and its process activation group (PAG). This, in turn, can help overall system performance. For example, if several work station users enter a transaction that involves updating and adding to several files, the system can perform better if the interactive jobs submit the request for the transaction to a single batch processing job.
  
  
• Data queues are a fast means of asynchronous communication between two jobs. Using a data queue to send and receive data requires less system resource than using database files, message queues, or data areas to send and receive data.
  
  
• You can send to, receive from, and retrieve a description of a data queue in any HLL program. This is done by calling the Send to a Data Queue (QSNDDTAQ), Receive from Data Queue (QRCVDTAQ), Retrieve Data Queue Message (QMHRDQM), Clear Data Queue (QCLRDTAQ), and Retrieve Data Queue Description (QMHQRDQD) APIs.
  
  
• When receiving data from a data queue, you can set a time-out such that the job waits until an entry arrives on the data queue. This is different from using the EOFDLY parameter on the Override Database File (OVRDBF) command, which causes the job to be activated whenever the delay time ends.
  
  
• More than one job can receive data from the same data queue. This is an advantage in certain applications where the number of entries to be processed is greater than one job can handle within the desired performance restraints. For example, if several printers are available to print orders, several interactive jobs could send requests to a single data queue. A separate job for each printer could receive data from the data queue in first-in-first-out (FIFO), last-in-first-out (LIFO), or keyed-queue order.
  
  
• Data queues have the ability to attach a sender ID to each message being placed on the queue. The sender ID, an attribute of the data queue which is established when the queue is created, contains the qualified job name and current user profile.