Data queues are used as overflow files within DataThread. For fine-tuning of the system, it may be desirable to have multiple data queues, especially when your application's files have large record lengths (fat files).
The space needed for each entry in the data queue is equal to two times the record length plus a fixed overhead amount (200 bytes or so, depending on the file). Therefore, the maximum queue length specified on the data queue should be large enough to hold entries for the file with the largest record length.
If only one queue is used, however, this queue must be big enough to hold the largest record size. Since data queue entries occupy the maximum entry length regardless of the actual entry size, files with a smaller record size consume a large amount of wasted space.
The program "System Parameters and Settings" (option 12 on the DataThread Menu) is used to maintain the system's data queues. In this program, each parameter beginning with the name IDTLOGQ and optionally followed by a prefix of one character, specifies a data queue. By default, the primary data queue is called IDTLOGQ, and is represented by the entry of that name, with no letter suffix.
The maximum size of each entry, as noted above, will determine which files' entries will fit in the queue.
Note: For complete details, see the DataThread Administrator's Guide.