Understanding Unsigned Writes

While the most common data entry objects support electronic signature, there are ways to write to a tag without capturing a signature. This is called an unsigned write.    The application developer can specify whether to allow these writes to update the database (accept) or to block (reject) them on a tag-by-tag basis. Unsigned writes can originate from:

• Scripts.
• Recipe downloads.
• Use of the Acknowledge All command on the Alarm Summary object or the AcknowledgeAllAlarms global subroutine.
• Global subroutines called from Scheduler scripts.
• Applications other than the WorkSpace, such as the Scheduler, Database Manager, or externally-written EDA applications.
• Writes to data sources that use expressions.
• Writes that originate from an iFIX 2.x or FIX32 node.

Accepting or Rejecting Unsigned Writes

You can configure a tag to accept or reject an unsigned write. In a secure signing environment, it is typical to reject unsigned writes; by default, the Reject Unsigned Writes option is selected.

The following fields are available in the Unsigned Writes section:

Accept – the tag accepts the write from an unsigned source.

Log – sends a message to the alarm system, indicating that the tag accepted an unsigned write. This field is available only when the Accept option is selected.

Reject – the tag rejects a write from an unsigned source in the same manner a write is rejected for a security violation. A message is sent to the alarm system to flag the violation. By default, this option is selected.

If a user changes a field of a tag that requires electronic signature directly in the Database Manager spreadsheet, that change is considered an unsigned write. Writes from the Database Manager tag configuration dialogs and SAC are always accepted, regardless of how you configure unsigned writes. Refer to the Changing Tag Values in the Database Manager Spreadsheet section in the Testing and Troubleshooting Electronic Signature chapter for details.

Values written from signature-disabled nodes to tags that require signature may be rejected. If an application has mixed nodes (some with the Electronic Signature option enabled, some with the option disabled), the application developer can restrict access to certain remote nodes to disallow writes from the disabled nodes, if necessary. For more information about disabled nodes, refer to Restricting Access from Remote Nodes. For more information about mixed nodes, refer to Using Multiple Versions of iFIX in a Network.

See Also