Set debug file before tracing SPL routines. (-687)

You may encounter the below error message from the application that access to your Informix database:

Set debug file before tracing SPL routines. (-687)

According to Informix finderr, the possible reason is:

A TRACE statement was executed before a SET DEBUG FILE statement. The destination of the output of the TRACE statement is unknown.
This error can also apply to the TRACE OFF statement.

But from our experience, you may need to check the following items if the above does not help:

a). Make sure the Informix user id is created as Windows user.

b). Assign that user to access the related folder or drive.