Invalid Metadata on Server Startup

[Anonymous user]

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In some cases when the ClearSCADA server turns pink to indicate an error starting up, you may be prompted with the error "The dynamic classes for one or more modules failed to load. See database log file for details". This is a form of Metadata error.

Metadata errors are related to database fields - often extra database fields - and can be related to duplicate field names being defined. The simplest example of this is when you have defined a custom database field which has the same name as an existing field in the table for a particular class. The server config tool should pick this up, but if the registry is modified directly, then it will cause a the server to ignore that field on startup.

A more serious metadata error can occur where incorrect driver declarations are present such that when the server starts up, the error displayed above is shown. This has been seen in the case of SDK drivers where the user incorrectly registers the driver dll in the system causing two instances of the driver definitions in the registry.

Extract from log files that indicated this problem:

10-MAY-2005 06:34:39.154 [KB:SDK] Error parsing D:\Program Files\Control Microsystems\ClearSCADA\SDKTrio.dll.xml - Failed to open file

The SDK interface could not open the .dll.xml file as it did not exist. The file should have been just .xml but this entry was added incorrectly by the user when trying to register the SDK Trio radio diagnostics driver.

Deleting the incorrect registry entry for the duplicate trio driver and restarting the server fixed the problem.

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