Alex McHugh wrote:

> Op-data is best because it's persistent only for the life of the operation,
> saving the hassle of checking if the driver-scope variable needs to be
> updated to reflect the current object.

On the other hand operation-data bloats the trace, especially if it contains
long text parts or serialized XML and is harder to access sometimes because
depending on context you might need to read it into a variable first before
actually being able to use it in a token.

To reliably clear out values from previous events, use different variables per
channel and set them to an empty or initial value in the first event transform
of each channel. If you already need it in IT for publisher events, set it in
first IT but make sure not to re-initialze on query/instance operations.