In update events, record the old value of the field to be updated.

[greatmazinger]

This was how it worked in Elephant Tracks 1. Currently, I'm not tracing this since I'm not sure how to access the fields of the instrumented object in Javassits.

[greatmazinger]

Leaving this open, but this doesn't seem possible. OTOH, I don't know if there's a need for tracing the old value as this should be easily derived from the trace.