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Refer also to the companion DTAQ_CLEAR, DTAQ_RECEIVE and DTAQ_SEND activities that allows you to send and receive data to and from and to perform other operations on a named data queue.
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Note: Data queues are persistent objects, but their data content can be lost or corrupted during a system failure. Backup, recovery and maintenance of data queues used in your LANSA Composer solution is your responsibility – you should make provision for this in your implementation plans. |
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| false | title | Note | : Unlike many other iterator activities, this activity will iterate indefinitely unless you take specific action in the iterator block to exit the iteration. It is designed to be used in a potentially long running processing sequence that perpetually waits on a message arriving at the specified message queue and then processes the message or initiates another processing sequence to process the message. For more information refer to Considerations for Extended Duration Processing Sequences . |
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- The DTAQLIB parameter is not used and its value will be ignored. (You may use the DTAQPATH parameter to specify a location for the data queue, if required.)
- Data queues are stored in pairs of files in the Windows server file system with .EDQ and .LDQ file extensions. The .EDQ file contains the data queue definition and entries. The .LDQ files are used to logically lock the data queue during receive operations. The file names are determined by the LANSA run-time support used by this activity. The files can be manually cleared or deleted by deleting the associated files. Alternatively the DTAQ_CLEAR activity may be used for this purpose.
- The location of the .EDQ and .LDQ data queue storage files is determined by the value of the DTAQPATH parameter. Refer to that parameter description for further information.
- Refer to the description of the DTAQ_SEND activity for more complete Windows Server Platform Notes relating to the suite of DTAQ activities.
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Note | : On Windows servers, the specific implementation used means that the activity is unable to handle certain types of exceptions that may be considered unexceptional in other circumstances. In such cases the processing sequence containing the activity may simply end abnormally without logging diagnostic information in the Processing Sequence log. This behavior differs from most other LANSA Composer activities and from the IBM i IBM i implementation of this activity. |
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You should be aware of this possibility and be prepared to diagnose such issues in other ways. For example, the x_err.log generated by the LANSA run-time may assist with diagnosing such conditions. |
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