Applies To:
  • CitectSCADA 5.xx

Citect is being used as a DDE Server. The DDE Client is set up to use the DDE conversation of Citect (the DDE topic) and Variable (the DDE service). It was found that, under heavy I/O Server load, Citect may crash after a few hours. Why is this? 

The fix will prevent Citect from crashing when the IO Server is under heavy load. As a side issue, if the I/O Server is running under heavy load check KB article Q2326 ("The Need for Speed - Citect Performance Tuning") for ways to improve performance. Another common cause of high I/O Server loading is the use of a large number of cicode tag writes in loops without any sleeps between them. Cicode tag writes have priority over cicode tag reads in Citect 5.21 and later versions. This means that the Sleep function should be used in cicode loops containing tag writes, particularly if there are a large number of tag writes.

This may be a problem CIT has confirmed in Citect for Windows versions 5.xx. This problem has been fixed in Citect version 5.21 Service Pack G.