Thanks to all for your suggestions on timestamp. I have two timestamps (start and end) and i have to increment both to avoid duplicate values and this can be too much of man-handling the timestamps.
I am therefore using a new column that increments with every call.
Thanks about the precision too. I did notice that even though it's declared for (6) digits the last 4 are always '0000' and the duplicates are always on the first 2. I initially wondered how two consecutive calls can have same timestamp upto 6digits of seconds (unless TD engine is running on super computer), now i know it's only precise upto .00 only (and not until 0.000000)