If you get at least one of the following messages, this indicates that messages are getting lost in WinCC. These messages are to be found, for example, as entries in the WinCC LOG files in the "Diagnostics" directory:

• ALGRT : Transfer buffer too small
• ALGRT : TagQueue overflow
• ALGRT : Messages are lost

One remedy here is to enlarge the "Queue". You make this change in "Regedit".

IMPORTANT
As a general rule, no warranty can be provided for direct changes made to the Registry, because this is the sole responsibility of the user. In any event, you are advised to make a backup of the Registry before undertaking the actions described here. Furthermore, these settings are computer-specific.  This means that when you copy the project to another computer, you must make the settings again.

Use the following procedure:

1. "Start > Run...", enter "regedit".
2. Search for the code:
   HKEY_LOCAL_MACHINE\SOFTWARE\SIEMENS\WINCC\Alarm Logging\CONSTANTS
3. Search for the name " InputQueue". If this entry does not exist, enter a new value (right-click -> "New > DWORD value").
4. Enter the following value or change the existing value accordingly:
   InputQueue ="10000"
   
   
   Fig. 01
   
   The default value for the queue entries is 1500 in Alarm Logging. If you get the above-mentioned messages, you can increase the value, as in our example, to 10000.

This remedy only helps in the case of a temporary overload of the system, for example at system start-up. In the case of permanent system overload, the error messages are just delayed.

Note:
In the WinCC Information System, under "General Information > Performance Data > Message System", there is an indication of the "message load without loss".