When you enable the Use On-The-Fly Logging option on the Logging Options tab of the Database Options dialog box, the process models progressively log result data concurrently with the execution instead of waiting until UUT testing completes. The database logging plug-in uses the Model Plugin – OnTheFly Step Results entry point sequence to process the step results. The final data TestStand logs is almost identical to the data the process model generates at the end of execution.

When you use this option, you can use the Database Viewer application to view the data in the database tables while the sequence executes. Enable the Discard Results or Disable Results when not Required by Model option in the Model Options dialog box to conserve memory by discarding step results after TestStand logs each result.

When you use on-the-fly database logging with a schema that uses a stored procedure or command statements that do not use the INSERT command, you cannot define constraints for foreign keys in step result statements that reference primary keys in UUT results. Defining constraints for these types of foreign keys generates an error because the on-the-fly database logger cannot execute the statement to create the record that contains the primary key before executing the statement to create the record that contains the foreign key.

The Generic Recordset (NI) and TS 2.x–4.0 Generic Recordset (NI) database schemas use the TOP 1 clause in the command text for all statements, as the following example shows, to improve performance when logging results to a database by preventing the recordset from accessing existing records in the database:

SELECT TOP 1 * FROM <TABLE NAME>

This performance improvement is useful when you enable the Use On-The-Fly Logging option for database files larger than 500 MB.