Applies To:
  • CitectSCADA 6.XX
  • CitectHMI 6.XX

CitectSCADA terminals which use the [CtEdit]Copy or [CtEdit]Run parameter to refer to a common or master version of a project may experience the hardware alarm "page.rdb _variable.rdb mismatch". The remote terminals will return this hardware alarm if a compile is performed on the master copy of a project, which exists in the location referred to by the [CtEdit]Copy or [CtEdit]Run parameter, and this project uses an OID tag-based driver. 

The hardware alarm will occur when all of the following is configured:
 - An OID tag-based driver (eg ABCLX) is used to communicate to an IO device, and
 - A tag from this IO device is in use (eg displayed on a page), and
 - The [CtEdit]Copy parameter is used on CitectSCADA terminals to point to a master project directory, or the system uses a common run directory.

The following sequence of actions will produce the hardware alarm "page.rdb _variable.rdb mismatch":
1. Shutdown CitectSCADA runtime (if running) on the machine with the master project
2. Compile the master copy of the project (note: no actual modifications need to be made to the project)
3. On a remote CitectSCADA runtime, without restarting, attempt to browse to a page where a tag using the OID tag-based driver is displayed.

The page will fail to be displayed and the above hardware alarm will become active.

This behaviour is related to the protection measures introduced in version 6.00 to prevent project mismatches when using OID tag-based drivers. This protection exists for good reason. If changes are made to pages which display OID tag-based driver values then the likelihood of the incorrect tag being displayed is significant. The user would also be unaware of the mismatch, which is potentially dangerous. For this reason, the ability to then display such pages on the remote PC is disabled. The remote machine must first have CitectSCADA runtime shut down and the latest project rdb (runtime database) files copied across, either by manually restoring or just relying on the [CtEdit]Copy parameter to copy them during a restart of CitectSCADA runtime.

It is possible to disable this particular protection measure by setting the parameter [Page]PageCheckDBFChange=0, however for the reasons outlined above this is generally not recommended.

For further information on OID tag-based drivers, refer to articles Q3657 and Q4074.

OID, page, variable, rdb, mismatch, copy, run